Clear Voice Denoiser by Reference

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Clear Voice

DENOISER-BY-REFERENCEAutomatic Stable Noise Reduction software

USER'S GUIDE

Voice of the Future

SpeechTechnologyCenter


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Clear Voice Denoiser-by-ReferenceUsers Guide

Speech Technology CenterSaint Petersburg, Russia

Copyright

Copyright 1999, 2000 by Speech Technology Center Limited (STC Ltd.). All rights reserved. ClearDenoiser-by-Reference in a part or as a whole may be used according to the corresponding licensreceive more copies or other information, please contact STC.

Disclaimer

Speech Technology Center accepts no liability whatsoever for any loss or injury incurred by the ownby any third party while using this Clear Voice Denoiser-by-Reference and specif ically disclaims anwarranties, merchantability or fitness for any particular purpose. The contents of the Clear Voice Denby-Reference and Users Guide are subject to change without notice.


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Contents

CONTENTS .........................................................................................................................................................

PREFACE.............................................................................................................................................................

CLEARVOICE FAMILY PRODUCTS..................................................................................................................

CLEARVOICE DENOISER-BY-REFERENCE ALGORITHM.............................................................................

CLEAR VOICE DENOISER-BY-REFERENCE SOFTWARE...........................................................

HOW TO USE CLEARVOICE DENOISER-BY-REFERENCE SOFTWARE ........................................................

CONTROL PANEL TOOLBAR............................................................................................................................

CHOOSING A SOUND FILE................................................................................................................................

SOUND FILE PROCESSING.................................................................................................................................

SOUND PLAYBACK............................................................................................................................................

WAVEFORM VIEWING......................................................................................................................................

EDITING OF THE SIGNAL PROCESSING FILTERPARAMETERS....................................................................


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TUNINGNOISE REDUCTION DEGREE.............................................................................................................

TYPICAL FILTER SETTINGS..............................................................................................................................

MANUAL ADJUSTMENT OF

NOISE

REDUCTION

FILTER

...............................................................................RETURN TO DEFAULT FILTER PERFORMANCE...............................................................................................

OPTIONS.............................................................................................................................................................

MUSIC APPLICATIONS......................................................................................................................................

TROUBLESHOOTING.....................................................................................................................................

USER SUPPORT................................................................................................................................................


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Preface

Clear Voice family productsSTC propose to the users an excellent set of software tools for noise cancellation and signalenhancement for noisy sound files. ClearVoice family products include Denoiser, Denoiser-byReference and Declicker.

Denoiseris intended to remove automatically slow varying background noise and partiallynarrowband noise (bad channel, office and industrial noise, traffic noise, etc.). It is the bestmeans to enhance poor quality speech sound recordings (e.g. real life sound reporting, etc.).

Denoiser-by-Reference is intended to remove automatically with minimal manual controlstable background noise and partially narrowband noise (vinyl plates side-effects, tape hiss,etc.). It is the best means to remove background noise in old sound archives.

Declickeris intended to remove automatically clicks (spike-like or pulse-like noise). It is best means to remove sound sandfrom recordings in old sound archives.The algorithmes realized in these software titles are also used in STC Sound Cleaner a

universal software for noise cancellation and speech enhancement.


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Clear Voice Denoiser-by-Reference algorithm

Clear Voice Denoiser-by-Reference introduces a proprietary, original, state-of-the-art algorithm

which is developed to remove background noise automatically from input signals and toenhance the sound quality of speech and other useful transmitted or pre-recorded signals.Denoiser-by-Reference algorithm in difference to other algorithms of Clear Voice package(Denoiser and Declicker) removes from the input signal constant or stable noise.

Denoiser-by-Reference enables the user to reduce an arbitrary broadband stable noise in audsignal (tape hiss, surface noise of vinyl records, concert hall acoustic noise, etc.). It isdeveloped mainly for the purpose of audio signal quality improvement in audio archives

processing and CD mastering.

The algorithm is intended for both inexperienced amateurs and advanced professionals and isfunctioning automatically but can be additionally manually adjusted for the very exact

correspondence to a specific applied task.Clear Voice can be implemented in real-time on embedded chips (customised large-scale ICsor standard DSP) or can be run on a PC under Windows in order to remove undesirable

environment noise from live or pre-recorded audio.


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Clear Voice Denoiser-by-Reference software

Denoiser-by-Reference Software is a perfect tool to restore noise-corrupted poor quality soundrecordings. It removes stable background noise and partially narrowband noise from processe

sound signals.

Advanteges:

Removes different kinds of music distortions of old music media (mostly MCs) withoutdistortions to speech signal. Effective against different background noises (vinyl plates side-effects, tape hiss, etc.)

The technology is fully automatic. It will find the selected background noise, recognise it remove distortions without any actions from the user side. Simple and user-friendly interface

The software works in Windows 95, 98, NT environment. For sound playback it can useSoundBlaster compatible soundboards or professional STC sound boards (STC-H118).


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Figure 1. The working window of Denoiser-by-Reference software.


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How to use Clear Voice Denoiser-by-Reference software

If you have a sound file having a stable background noise you can point out, you can get this

sound file (source file) cleared and have a new sound file with better speech quality afterprocessing by Denoiser-by-Reference software.Firstly, run DenoiserByReference.exe, then you will see the working window of Denoiser-by-

Reference software. (If you run the software for the first time you will be asked to enter theregistration data).

Using controls you can choose a sound file, process it, listen to source or processed sound,adjust noise cancellation filter parameters and to see the waveform of the sound signals.

Control Panel toolbar

On the top of the working screen you can see the toolbarControl Panelwith buttons. Clickingon the corresponding button you can select a required function of the software.


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Choosing a sound file

By using the software you can improve useful signal quality and reduce many types of noise fpreviously recorded 8/16 bit PCM mono or stereo *.wav sound files. To process a specific file

click on the button in the tool bar. Select the requirfile name by standard Windows means. In the field of the working window you see the chosen file name.

Figure 2. Control panel of Denoiser-by-Reference software.


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In the field in the working window you will see the name of the target sound filewith the processed, cleaned signal. The default name will be the name of the chosen sourcesound file with the adding of signs *_CLRbefore its file extension. You can change this name

and file location typing any new file name with the required path in the field.The processed sound file has standard PCM 16 bit Windows *.wav format. In the field you will see the name of the file containing noise pattern. To create noise pattern, you ha

to select (see waveform viewing below) a part of the waveform containing stable backgroundnoise (for example, in pauses between speech or music). After selecting the noise in thewaveform press button on the Control Panel. You can also load previously save

noise pattern by using button.

Sound file processing

Once you have opened a pre-recorded file and defined the appropriate noise file click on

button in . After several seconds you will have a processed sousignal of the source file in the target file.


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Clicking button you can stop processing. In this case target file contains only a of the processed file.

Sound playback

Play the sound before and after noise reduction. To play the original source sound click on

button (a green one) in tool bar.

To listen to the filtered sound after processing, click on button (a blue one

Pressing of button stops sound playback.

Waveform viewing

At the bottom of the working window you can see the waveform pictures of the sound files.Before processing you will see a waveform of the source file (green color).


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After processing you will see over the previous picture a waveform of the processed file (blue

color).

Figure 4. Waveform field with a waveform of a source audio signal.

Figure 3. Waveform field with a waveform of a source audio signal (green)

and of the processed signal (blue).


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Using the mouse pointer and left mouse button you can select in the waveform field any part othe sound files to listen to. Put the mouse pointer to the place of the desirable beginning of thpart to listen to and press the left mouse button. Move the pointer in the required direction

holding the mouse button pressed and release it at the palce, where you would like to finish thselection.This selection is showed in the waveform field by two adjustable vertical lines (markers) and b

the changed color of the picture between the markers. Clicking by right mouse button on the

Figure 5 . Waveform field with waveforms of a source audio signal. The selected part of the signals

shown by reverse colors (gray area).


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waveform field (or on button in toolbar) removes selectionmarkers from the waveform field.

If you work with of several files, you will have the waveform picture of the givenfile(s) in the waveform field after clicking twice the desirable file(s) in the list.

Editing of the Signal Processing Filter Parameters

Denoiser-by-Reference filter works automatically, but you can adjust filter performanceadditionally.

Clicking button or button returns all filter settings to theirdefault values.

Important: We recommend manual adjustment of filter control parameters only to advanced use

There are several ways to change noise suppression filter performance


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Tuning Noise Reduction Degree

You can adjust Noise reduction degree (or depth), i.e. quantity of the noise to be removed wit

all other parameters of the algorithm fixed. Speech and noise as usual have some similar signcomponents, sometimes Denoiser-by-Reference filter changes useful signal during noiseremoval. Not all such changes are acceptable for specific application or situation. So the usershould choose a trade-off between the most noise removal and the most natural speech signa

STC experts chose and set in Standardmode of Denoiser-by-Reference (default state when

button at panel is pressed) the optimized universalcombinations of allcontrol parameters of noise reduction filter. The only control which can be changed in this mo

is . It determines the genenoise suppression depth and the level of residual noise.In order to get the best compromise of noise level and speech quality for your noisy sound in

most simple way you can use slider in panel.


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This control works only if button is pressed. You can change the slider horizontaposition by mouse clicking to the left or to the right of the slider and adjust the total noisereduction degree (depth).

The most left position of the slider (value 1) corresponds to the most saved but a bit noisy resThe most right position (value 10) corresponds to the most severe noise suppression but withpossible loss in the useful signal quality (there may appear music noise). Typical noise

suppression for different slider positions and thecorresponding values are the following: 1 - 8d2 - 11dB,3 - 14dB, 4 - 18dB, 5- 21dB, 6 - 24dB, 7 - 27Db, 8-30dB, 9 - 35dB, 10 - 40dBTypically this Noise Reduction Degree slider should be in the center of the control field, and a

reasonable noise reduction is 14-23 dB. An acceptable value depends on the type of the sounand even on the used speaker or headphones and the distance between loudspeaker andlistener.


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Typical filter settings

The algorithm adjustment which is more sophisticated but standard for some specific signalscan be chosen after adjusting filter settings for several preliminary recorded files of the same

type. Click on button in panel. After that theCurrent settingfield will be active.Then you can choose some typical options, choosing available ready-made sets of filter setti

from List of the typical filter set-ups. To do it, choose a required set clicking the pointer i

the right part of this field in window. You will see the list of available types of settings.


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Clicking on the required settings name you load those settings into the filter and they are valid

until you change filter settings manually or load a new set of filter parameters. In regard totypical available settings we can say that music sound or sound files for acoustical CD with thvery high demands on output signal quality usually require different filter adjustment than

Figure 6. List of typical filter settings.


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speech signals for telecommunication tasks. The reason is that in telecommunicationapplications the main aim of signal processing is the maximal intelligibility improvement,whereas for music and entertainment application the sound naturalness is far more important

For example, for CD mastering sometimes CD quality 01 settings provides the user with a bitbetternoise reduction and more gentle processing of the useful signal for files with 44100Hzsampling rate. The same settings for speech signal at 8000Hz sampling rate and

telecommunication sound quality would provide a small audible echo and not the maximal noreduction degree.

button to the right from button load the sound file with a short so

example, for which the filter settings in the chosen set are the most reasonable. These examfiles are included only in the full professional delivery set.

In order to process source sound file with the new options click on button in.

For noise reduction in Automatic Speech Recognition (ASR) applications we recommend to tthe universal settings of mode as well some ofAutomatic speech recognition


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settings in the list. Usual Universalsettings may sometimes provide you with quite goodsubjective sound quality but at the same time with rather poor performance improvement for aspecific ASR engine. The best sound quality for human ear and computer earare usually rath

different. At STC web site you can find and look at a special demonstration kit Demo of ClearVoice for ASR applications . There are sound files and ASR engine which demonstrate methoof Clear Voice technology implementation for ASR tasks.

Manual adjustment of Noise Reduction Filter

We recommend to use the manual mode of adjustment only for advanced and fastidious userYou can change the options of the noise canceling filter in Manualmode by clicking on

button in the toolbar. This button is active only when button

in panel is pressed. After pressing button you will see


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Figure 7. Options field.


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In this field you can change any settings by clicking and moving by mouse pointer on controlClicking on the button confirms all new filter settingss and they are set for the currentfiltration process. In order to process the source sound file with the new filter options click on

button in tool bar. Clicking on button restores settings asthey were berore entering this field.

Return to default filter performance

Clicking button in tool bar or button in

panel returns all filter settings to their universal standard values.


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Options

This feature corresponds to the duration in samples of a piece of the source signal that is use

for processing. The bigger is Noise Detailduring signal processing, the better is noise reductBut at the same time biggerNoise detailvalues can provide with some audible echo effect.

Table 1. Typical & additionalFrame sizevalues

for various sampling rates of the source signal files

Sampling rate of source sound file

in Hz

Standard

value

Addi tio na l

values8000 Short ened standard Small, Standard

11025 Standard Shortened or Extended standa

16000 Standard Extended standard, Large

22050 Extended standard Extended standard, Large

44100 Large Extended standard,

Extra large


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In standard mode Noise Detailis set automatically according to the sampling rate of the soursignal. There is an approximate correspondence between Noise detaildegree and Frame sizein samples for signal processing: Extra small 60, small 130, shortened standard 260,

standard 500, extended standard 1000, large 2000, extra large 4000.

Denoiser-by-Reference suppression procedure has two modes of signal processing. The first

mode has a bit higher output sound quality. Experts can hear a msoftsound for high quality source signals without any artifacts in sounding.The second mode is about twice less demanding on calculating power and provides w

sufficiently high sound quality for many practical applications, in particular for signals withtelecommunication quality of sounding. For fastmode some very soft clicks may sometimesoccur, especially in emptyfrequency bands. This mode may be useful to evaluate the algorith

acceptability in applications with limited calculation recourses.


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This option enables users to realize additional Low pass and High pass frequency filters.Lowpass filtering is the simplest way to reduce or eliminate the low frequency hum, backgrou

mumble and babble. Highpass filtering allows to eliminate or reduce harmful hiss or high-tonasqueak and creak. Though the general procedure suppresses low and high frequencycomponents of noise the user sometimes can get improved results while using these features

minimize the impact of noise by means of excluding frequencies containing noise.Using < LF frequency> you can specify frequency of Low pass filter. For lower frequencies thefilter envelope has a fast uniform roll-off to 0Hz.

Using < HF frequency> you can specify frequency of Highpass filter. For higher frequencies th

filter envelope has a fast uniform roll-off to the half of the current sampling rate in Hz.The frequency boundaries and amplifying of additional filters should be chosen by ear in

accordance with signal quality and type.


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Table 2. Typical values of HF and LF parameters.

Type of the sound signal LF frequency in Hz HF frequency in Hz

Telephone conversation 200 3400

Tape record 100 4000 7000

Dictaphone record 200 3600

CD quality sound 70 10000-15000

Master CD 20 20000

By mouse clicking you can make this filter option active (a tick in the box) or passive (a blankbox).

This algorithm feature is turned on by default Clear Voice settings and corresponds to activatiof the additional suppression of narrowband or harmonic (Sin-wave like) components of thehindrances.

Without this feature being activated attenuation of the tonal noise components in processedsound is equal to Noise Reduction Depth, which is set by option in


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panel (typically 17-20 dB). Activating of this feature provides with pure tonesattenuation by 50-75 dB.When activated, this option enables the procedure to remove additionally bells, horns, power

supply hum, buzz, whistle and similar tonal sounds, being in sound signal to filter. So thatDenoiser-by-Reference can reduce significantly these tonal hindrances the frequency andamplitude of their harmonics is to vary relatively slow. The faster tonal hindrances are changin

the less parameter should be in panel.Sometimes such additional tonal sounds components reduction is not desirable, because themay be components of the useful signal (for example, slow music). In this case this option

should be turned off.The more is, the more effective this option works is and vice versa.

This control corresponds to Maximal Noise Suppression Depth (in dB scale), that is limitingthreshold for total noise reduction degree. This control determines the minimal possible residunoise level in output signal. It reflects the target improvements in decibels for Signal-to-Noise-

Ratio for sound before and after processing.


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Broadband noise is reducing in the processed source sound signal not more then by this valuThis control option is used to reduce the effect of residual disturbances and in particular socalled music noise appearance in the output sound signal. If all other options are fixed, then

reducing of this parameter increases the level of audible residual noise by 1 dB for 1 unit ofparameter change. In other words: noise is to be half as much, if is increased twice. Ifis decreased, then residual background noise is getting audibly more strong, but unifo

and homogeneous, in addition output signal has less and less audible artifacts, i.e. short andsoft bells and tones, which might be heard in pauses. If is increased, then residualbackground noise is getting less audible, but in the same time it is getting less homogeneou

and less suitable in aural quality. In extreme cases it may appear audible, so called musicalnoise - a random combination of short different tones, as if somebody is randomly striking

different piano keys. Especially this effect is noticeable in pauses.As usual it is reasonable to change this parameter in the range +-3/6 dB from standard valueorder to achieve a little more effective noise reduction results. Note, that 6 dB corresponds tothe change of noise level in 2 times. Range of is 0-60.

Simultaneously with should be changed control. Both these optionsshould have got some increasement or some decreasement. It is reasonable to use as a


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starting point for the choice of the best parameter value, the value in standard mode, which isset when , value 4 is pressed.

The meaning of this control corresponds to Strength of noise reduction. This parameterdetermines the amount of noise, which the filter attempts to eliminate from the processed audfile. The previous control bounds the realization of noise suppression on the level of

value in dB. The more is, the more noise reduction is, but in the same time thmore distortions are put into the residual useful sound signal, because weak, noise-like speecomponents are suppressed, too. The best results are obtained if used noise reduction degre

matches the real proportion between undesirable noise and useful signal.Denoiser-by-Reference noise reduction algorithm leaves without changes all speechcomponents that are bigger then some threshold and gives quite significant noise reduction fo

speech components, which have the amplitude level less then this threshold. CurrentSuppression value determines the location of this threshold.There should be quite strong dependence between this and the previous parameters optimal

values. When Suppression is arisen from 1 to 40 in the same time Maxshould be usually


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increased, too, from 8 to 50, and vice versa. and controls have big influence on real noise reduction intensity, too. It is reasonable to useas a starting point for the choice of the best parameter value, the value in standard mode, whi

is set when , value 4 is pressed.

This parameter determines the difference (that is contrast) in noise reduction degree for loud

and soft parts of the processed signal. The more the value of the Contrast parameter is, themore difference between noise reduction degree for soft parts of the input signal in comparisowith loud ones is. Typically, Contrast should have maximal value. But lower values could

sometimes provide gentler sounding of output signal.

This control determines the smoothness in frequency of the spectrum of output sound signal.

This feature is used to reduce the spectral homogeneity of the residual noise. If this parameteis too low, the processed signal will sound a bit rough and mechanical. Sometimes it will becorrupted by a specific disturbance, so called musical noise - a random combination of short


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different tones, as if somebody is randomly striking different piano keys. If the spectralsmoothing is too large, the noise reduction degree is bigger in total, but is less detailed, and output signal might sound hollow and lifeless.

The bigger this parameter is, the less value should be set.The maximal values of this parameter may be used to reduce the iron in the sounding. Rangechanging is 1-40. It is reasonable to use as a starting point for the choice of the best paramet

value, the value in standard mode, which is set when , value 4 is pressed.

This feature is used to reduce the time uniformity and homogeneity of the residual noise. If th

parameter is too low, the processed signal will sound a bit mechanical. Sometimes it will becorrupted by a specific disturbance, so called musical noise - a random combination of shortdifferent tones, as if somebody is randomly striking different piano keys. If the time smoothing

too large, the noise reduction degree is less and an output signal might sound with a small eeffect. The parameter is useful to decrease the hardness and iron qualityin the sound. Rangechanging is 0-9. It is reasonable to use as a starting point for the choice of the best paramete

value, the value in standard mode, which is set when , value 4 is pressed.


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Noise reduction degree

This control allows setting of all the current filter options to their defaults values for Universalmode.

For this aim in the panel Noise reduction degree set the required va

of the total noise reduction degree by clicking button. If 0, then default parameters set is used, and all parameters are taken from panel. If 1-10, all other parameters of thisworking control panel are set to values, which correspond to default parameters set in Univermode. The standard value 1 corresponds to minimal noise reduction degree and provides the

most saved and natural input signal with typical noise reduction by 8dB. The value 10 providetypical noise reduction by 40 dB but sometimes the output sound signal could have got somesmearing, nibblingor other audible corruption. So this general Noise Reduction Degree scale

has at the one pole (value 1) The best useful signal quality and small level of noisesuppression and at the second pole (value 10) A bit corrupted useful signal and very large levof noise suppression.

Recommended default standard value is equal to 3-5.


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Save settings to the file

You can save your own filter options in the new *.set file using button After pressing it you will see the dialog window .

In dialog box fields you will have information corresponding to the last saved *.set file. Pleasetype a new file name and a title of your new settings composition. This title will be used in thelist of available set-ups after pressing button in panel.

If you want you can save an example of the sound file, which is most suitable for the given filteoptions set. To do it, type a name of the example file in the third line of the dialog box. When the fields are filled, press button.

Automatic Speech Recognition applications

Figure 8. Dialog box of settings file saving.


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Clear Voice Denoiser-by-Reference algorithm can be used as a front-end preprocessor of inpulive sound signal or pre-recorded sound file for applications of automatic speech, speaker orlanguage recognition. In such a case, it can dramatically increase the success rate of any

engine working in noisy background.It is important to note that usual Universalnoise canceling filter options are, in general, not sogood for automatic speech recognition application. Depending on specific front-end ASR

procedures using of special filter tuning can sometimes significantly increase the positive effeIt confirms the fact that subjective good speech quality (as perceived by a human ear) is notneccessarily good for a technical application.

For such tuning you should use Professionalmode of the filter adjustment. Click on

button in panel. After that list of set-ups will bactive. Then you should choose an available ready-made set of filter settings from this list by

clicking the pointer in the right part of this display.Clicking the name of a set, you load those settings into the filter and they are valid until youchange filter settings manually or load a new set of filter parameters. For ASR we recommend


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to use ONLYAutomatic speech Recognition. ModeXXsettings set. You can try to get evenbetter results by slightly changing values of some settings (especially Max, Suppression,Smoothing in frequency and time).

In order to process the source sound file with the new options click button in.

Music applications

Clear Voice Denoiser-by-Reference algorithm can be successfully used for CD mastering and

processing of the relatively high-quality records of music and speech. It is important to note tstandard Universalnoise canceling filter setting may be, in general, not so good for such tasAfter background noise reduction, there might occur some loss in speech and music quality,

appear several slightly heard music noise orecho. Often using special filter tuning cansignificantly increase the output sound quality. Only big experience of practical filter adjustmecan help you to find out the filter options with really maximal positive effect and minimal residu

noise.


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For such tuning you should use Professionalmode of the filter adjustment. Click


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Figure 9. List of typical filter settings.


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Troubleshooting

Little or no sound output

Check the level of the input and output sound files in the waveform picture. They are to havenon-zero amplitude values.Check the current volume control level at the bottom of the working window of Denoiser

Software . The slider should be at the right side of the sca

See How to Set the Output Level.

Make sure the speaker or line-out cable is plugged into the correct output on your sound boarCheck that the speaker has electrical power and that the switch is turn on.

How to Set the Output Level.If the sound level is too low or too high, you can change it by means of your MS Windows OStools and in Denoiser Software directly.


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1. Check the volume control level in your MS Windows OS. Set the playback level properly:Click Start button, Programs, Accessories, Multimedia and Volume Control.Make sure that Wave Output does NOT have Mute checked, that the volume is high enough

and that the balance control is in the center. Check that Volume Control level (in the far lefthigh enough and that the balance control is in the center. Also, make sure that the connectiobeing used for input, usually Line-In or Microphone , is NOT selected to avoid playing the

unprocessed and the processed audio simultaneously.2. Check the current volume control level at the bottom of the working window of Denoiser

Software . The slider should be at the right side of the sca

Voice Output is Distorted1. Check that the original sound in the source file has not too high level. To do it, listen to the

source file clicking a green button in tool bar.

2 If you use mode, check that parameter is not too high. See

Manual Adjustment of Noise Reduction.


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3.Check Sound Board Mixer options in your MS Windows OS. Click Start button, ProgramsAccessories, Multimedia and Volume Control.Make sure that Wave Output does NOT have Mute checked, that the volume is high enough

and that the balance control is in the center. Check that Volume Control level (far left) is higenough. Also, make sure that the connection being used for input, usually Line-In orMicrophone, is NOT selected to avoid playing the unprocessed and the processed audio

simultaneously.

4.Set Denoiser parameters to default values by clicking button.5. If after all aforementioned operations the output sound has not good enough quality and you

are sure that it is an effect of harmful noise, you can try to change standard noise cancelling

filter parameters in order to get better results. See Editing of the Signal Processing FilterParameters.Note: For some noisy speech files with high sampling rate (44100 Hz or higher)

better filtering results may be provided by setting value in option.


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User Support

STC developers are always ready to assist you.

In case of any questions, please dont hesitate to contact us.

WWW: http://www.speechpro.com

E-mail: [email protected]: +7 812 3279297Phone: +7 812 3258848

We hope that you would like our product! Please note that we are always ready to develop ancustomized software for you. Any questions on our products and development costs should b

addressed to our Sales department:e-mail: [email protected]).

Documents

Clear Voice Denoiser by Reference