Copyright Tasko & Finan 2008 Instrumentation for “Dummies” Supporting Clinical Practice With Simple, Low-Cost Technology Stephen Tasko Ph.D. CCC-SLP Western

Copyright Tasko & Finan 2008Copyright Tasko & Finan 2008

Instrumentation for Instrumentation for “Dummies”“Dummies”

Supporting Clinical Practice Supporting Clinical Practice With Simple, Low-Cost With Simple, Low-Cost

TechnologyTechnology

Stephen Tasko Ph.D. CCC-SLPWestern Michigan UniversityKalamazoo MI

Donald Finan Ph.D.University of Northern Colorado

http://homepages.wmich.edu/~staskohttp://homepages.wmich.edu/~stasko


TopicsTopics

Why focus this talk on high quality sound Why focus this talk on high quality sound recording?recording?

Sound recording 101Sound recording 101

Available recording devicesAvailable recording devices


Instrumentation and Instrumentation and TechnologyTechnology

Love it or hate it?Love it or hate it?


Why focus discussion on sound Why focus discussion on sound recording?recording?

High quality digital recordings can now be High quality digital recordings can now be made with fairly common devices at made with fairly common devices at relatively low costsrelatively low costs

In my view, as both a speech language In my view, as both a speech language pathologist and speech scientist, good pathologist and speech scientist, good sound recordings give the SLP the most sound recordings give the SLP the most “bang for the buck”“bang for the buck”


What high quality digital sound What high quality digital sound recording offers?recording offers?

Provides a permanent archive of client behaviorProvides a permanent archive of client behavior Can allow quick, easy access to samples to monitor Can allow quick, easy access to samples to monitor

client statusclient status Has face validityHas face validity Potential for more objective baseline and follow up Potential for more objective baseline and follow up

evaluationevaluation Can support and guide clinical decision makingCan support and guide clinical decision making Can serve to streamline and standardize assessment Can serve to streamline and standardize assessment

approaches approaches Allows an entrée intoAllows an entrée into

More quantitative instrumented analysisMore quantitative instrumented analysis Database development for clinician directed research on Database development for clinician directed research on

outcomesoutcomes


Sound Recording 101Sound Recording 101


Tasko’s rating systemTasko’s rating system

PreferablePreferable

Highly preferredHighly preferred

Not recommendedNot recommended

Strongly discouragedStrongly discouraged


Sound Frequency rangesSound Frequency ranges

Normal humans hearing 20 Hz – 20,000 HzNormal humans hearing 20 Hz – 20,000 Hz

Human speech ~ 50 Hz – 8000 HzHuman speech ~ 50 Hz – 8000 Hz

Standard phone circuits ~ 300 - 3000 HzStandard phone circuits ~ 300 - 3000 Hz


Frequency Range for SpeechFrequency Range for Speech

For good audibility, we need to be sure our recordings capture the whole frequency range for speech


What are you using the What are you using the recording for?recording for?


Components of Sound RecordingComponents of Sound Recording

microphone Pre-amplifier(maybe)

Cassette recorder



microphone Pre-amplifier(maybe)

or


The quality of the recording is The quality of the recording is only as good as its weakest only as good as its weakest

componentcomponent



Microphone

Digital Recording Device•Digitization of sound•Storing of sound as file

Playback ability•Amplifier-Speaker•Headset

+/- amplifier


How does tape recording differ How does tape recording differ from digital recording?from digital recording?

Analog (tape) recordingAnalog (tape) recordingAcquires a continuously varying signalAcquires a continuously varying signal

Digital recordingDigital recordingAcquires a string of discrete numbersAcquires a string of discrete numbers


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Analog (Continuous)

Digital (Discrete)


Digital RecordingDigital Recording

Since sound is converted to a string of numbers, Since sound is converted to a string of numbers, two issues have an influence on recording two issues have an influence on recording

accuracy/fidelityaccuracy/fidelity

1. How often does the device “grab” a number? 1. How often does the device “grab” a number? Sampling rate/frequencySampling rate/frequency

2. How much precision is used when number 2. How much precision is used when number recording?recording?Quantization levelQuantization level


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Sampling Rate

High

Low


Sampling TheoremSampling Theorem

If a band-limited signal is sampled at a rate If a band-limited signal is sampled at a rate that is at least twice as high as the highest that is at least twice as high as the highest frequency in the signal, no information is frequency in the signal, no information is lost and the original signal can be exactly lost and the original signal can be exactly reconstructed from the samplesreconstructed from the samples


Nyquist frequencyNyquist frequency

Maximum frequency contained in the Maximum frequency contained in the signal of interestsignal of interest

Humans hear < 20 KHzHumans hear < 20 KHzHuman speech < 7-8 KHzHuman speech < 7-8 KHzPhone circuits < 3.2 KHzPhone circuits < 3.2 KHz


Simple RuleSimple Rule

sample rate/frequency must be 2X highest frequency of interest

For speech it must be at least 16000 Hz


Digital Devices: Common sample ratesDigital Devices: Common sample rates

5,562 Hz5,562 Hz

11,025 Hz11,025 Hz

22,050 Hz22,050 Hz

44,100 Hz44,100 Hz CD qualityCD quality Captures range of hearing Captures range of hearing

16 KHz

32 KHz

8 KHz

4 KHz

2 KHz


Loosing important parts of the “bandwidth”Loosing important parts of the “bandwidth” Possibility of “aliasing”Possibility of “aliasing”

Most sound cards have anti-aliasing filters Most sound cards have anti-aliasing filters Low-pass filters sound to prevent aliasingLow-pass filters sound to prevent aliasing However, now have a restricted bandwidthHowever, now have a restricted bandwidth

TAKE-HOME MESSAGETAKE-HOME MESSAGEDO NOT UNDERSAMPLE YOUR SIGNALDO NOT UNDERSAMPLE YOUR SIGNAL

Problems associated with poor Problems associated with poor selection of sample rateselection of sample rate

http://www.dsptutor.freeuk.com/aliasing/AliasingDemo.html

F= 7 KHzSF=16KHz

F=7 KHzSF=8 KHz


QuantizationQuantization

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Inchesless precise

millimetersmore precise


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0 2 4 6 8 10 12 14 16 18 20-2

-1.875-1.75

-1.625-1.5

-1.375-1.25

-1.125-1

-0.875-0.75

-0.625-0.5

-0.375-0.25

-0.1250

0.1250.25

0.3750.5

0.6250.75

0.8751

1.1251.25

1.3751.5

1.6251.75

1.8752

Quantization

High

Low



Expressed in “bits”Expressed in “bits” ↑↑ bits ~ bits ~ ↑↑ # of marks on the “ruler” = greater precision # of marks on the “ruler” = greater precision X bits/sample = 2X bits/sample = 2x x possible units of measurepossible units of measure For example,For example,

2 bit = 4 levels2 bit = 4 levels 4 bit = 16 levels4 bit = 16 levels 8 bit = 256 levels8 bit = 256 levels 12 bit=4096 levels12 bit=4096 levels 16 bit = 65536 levels16 bit = 65536 levels

http://www.cosc.canterbury.ac.nz/mukundan/covn/Quant.html



Expressed in “bits”Expressed in “bits” ↑↑ bits ~ bits ~ ↑↑ # of marks on the “ruler” = greater precision # of marks on the “ruler” = greater precision X bits/sample = 2X bits/sample = 2x x possible units of measurepossible units of measure For example,For example,

2 bit = 4 levels2 bit = 4 levels 4 bit = 16 levels4 bit = 16 levels 8 bit = 256 levels8 bit = 256 levels 12 bit=4096 levels12 bit=4096 levels 16 bit = 65536 levels 16 bit = 65536 levels


0 2 4 6 8 10 12 14 16 18 20-2

-1.875-1.75

-1.625-1.5

-1.375-1.25

-1.125-1

-0.875-0.75

-0.625-0.5

-0.375-0.25

-0.1250

0.1250.25

0.3750.5

0.6250.75

0.8751

1.1251.25

1.3751.5

1.6251.75

1.8752

00.250.50.7511.251.51.7522.252.52.7533.253.53.7544.254.54.7555.255.55.7566.256.56.7577.257.57.7588.258.58.7599.259.59.751010.2510.510.751111.2511.511.751212.2512.512.751313.2513.513.751414.2514.514.751515.2515.515.751616.2516.516.751717.2517.517.751818.2518.518.751919.2519.519.7520-2

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Low sampling rate

Low quantization

Low sampling rate

High quantization

High sampling rate

Low quantization


Checking your own computerChecking your own computer


Sound Fidelity vs. File SizeSound Fidelity vs. File Size

Digital memory is relatively cheapDigital memory is relatively cheap Good client records are invaluableGood client records are invaluable



Microphone



+/- amplifier


Digital File formatsDigital File formats

Mono vs. StereoMono vs. Stereo Alphabet SoupAlphabet Soup

.wav.wav .nsp.nsp .mp3.mp3 .mp4.mp4 .wma.wma .dss.dss .au.au etc, etc, etcetc, etc, etc


Digital File formatsDigital File formats

Uncompressed Formats Uncompressed Formats (Lossless)(Lossless)

All samples are retainedAll samples are retained What you record is what What you record is what

you getyou get Most common formatMost common format

““.wav” (PCM).wav” (PCM)

Compressed FormatsCompressed Formats algorithm used to reduce algorithm used to reduce

file size yet maintain good file size yet maintain good audibilityaudibility

Driven, in part, by music Driven, in part, by music industryindustry

Common FormatsCommon Formats .mp3, .wma, .dss.mp3, .wma, .dss

Effect on speech samples Effect on speech samples is not well knownis not well known



Microphone



+/- amplifier


The MicrophoneThe Microphone

Microphones Microphones Matter!!Matter!!


What (I think) you need to know What (I think) you need to know about microphone selectionabout microphone selection

Type of microphoneType of microphone

Underlying operationUnderlying operation

How it connects to other devicesHow it connects to other devices

Pick up patternsPick up patterns

Frequency ResponseFrequency Response


Microphones: Common TypesMicrophones: Common Types

HandheldHandheld

Built in to recorderBuilt in to recorder

Clip on/lavalierClip on/lavalierHead wornHead worn


Underlying operationUnderlying operation





Headset Microphone PlacementHeadset Microphone Placement


Microphone Frequency ResponseMicrophone Frequency Response

What is a frequency response curve?What is a frequency response curve?Graph that shows how the microphone Graph that shows how the microphone

responds over a range of frequenciesresponds over a range of frequenciesLook for a relatively flat line within the Look for a relatively flat line within the

frequency range for speechfrequency range for speech


Frequency Response CurveFrequency Response Curve



Speech Range




To pre-amplify or not to pre-amplifyTo pre-amplify or not to pre-amplify

Great variation in size of Great variation in size of signal coming from micssignal coming from mics

May need to amplify the May need to amplify the mic signal so it is heard mic signal so it is heard by the recording deviceby the recording device

OftenOften Best mics put out small Best mics put out small

signalssignals Cheapest mics put out Cheapest mics put out

largest signalslargest signals


A Tasko Seal of ApprovalA Tasko Seal of Approval

Audio-Technica ATM75 (without powerpack!! - cheaper)Audio-Technica ATM75 (without powerpack!! - cheaper)

FeaturesFeatures Condensor type HeadwornCondensor type Headworn DirectionalDirectional Acceptable frequency responseAcceptable frequency response Decent sized output signalDecent sized output signal

amplification not typically necessaryamplification not typically necessary Can be purchased with a variety of connectorsCan be purchased with a variety of connectors REASONABLY PRICED (~ $99)REASONABLY PRICED (~ $99)


Audio Technica ATM75Audio Technica ATM75

http://www.soundprofessionals.com/cgi-bin/gold/item/ATM75-SP-NP


Recording IssuesRecording Issues

Keep mic-mouth distance relatively Keep mic-mouth distance relatively constant within and across recording constant within and across recording sessionssessions

Setting your recording levels is very Setting your recording levels is very importantimportant

You really want a device that monitors the You really want a device that monitors the recording levelrecording level


Apply the “Goldilocks” RuleApply the “Goldilocks” Rule


That recording level is just tooooo low!That recording level is just tooooo low!

Environmental noise becomes an issueEnvironmental noise becomes an issueDoes not take advantage of the precision Does not take advantage of the precision

of the recording deviceof the recording device

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That recording level is just tooooo high!That recording level is just tooooo high!

Signal will be “clipped” resulting in distortionSignal will be “clipped” resulting in distortionTruncates the largest amplitude Truncates the largest amplitude

componentscomponents

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Microphone



+/- amplifier


A brief survey of digital recording A brief survey of digital recording devicesdevices

Personal Recording DevicesPersonal Recording Devices Digital dictaphonesDigital dictaphones iPodsiPods PDAs (Palms, Smartphones) PDAs (Palms, Smartphones)

““Professional” Grade DevicesProfessional” Grade Devices Digital equivalents to the pro-duty cassette recordersDigital equivalents to the pro-duty cassette recorders Devices developed primarily for music industryDevices developed primarily for music industry

The PC (or Mac)The PC (or Mac) LaptopLaptop DesktopDesktop


Questions to ask about portable Questions to ask about portable recording devicesrecording devices

Basic recording performance questionsBasic recording performance questionsAre the sampling rate options appropriate Are the sampling rate options appropriate

for speech recording?for speech recording? Is the quantization rate appropriate for Is the quantization rate appropriate for

speech recording?speech recording? Is the overall frequency response of the Is the overall frequency response of the

device acceptable for speech recording?device acceptable for speech recording?



Microphone/recording level related questionsMicrophone/recording level related questionsCan an external microphone be used?Can an external microphone be used?What kind of connectors are needed? What kind of connectors are needed? Will you need a mic amplifier?Will you need a mic amplifier?Can recording levels be adjusted?Can recording levels be adjusted?Can recording levels be monitored?Can recording levels be monitored?



Data Storage/Transfer QuestionsData Storage/Transfer Questions What file format is used to save the data?What file format is used to save the data? Can it record in a lossless format?Can it record in a lossless format? What is the recording capacity of the system What is the recording capacity of the system

with the preferred recording settings?with the preferred recording settings? Does it have only built in memory or can you use Does it have only built in memory or can you use

standard memory media (e.g. SD cards)?standard memory media (e.g. SD cards)? How easy is it to move the recordings off the How easy is it to move the recordings off the

device and onto a PC for archiving (i.e. USB)?device and onto a PC for archiving (i.e. USB)?



Human Factors QuestionsHuman Factors QuestionsCan you easily play back recordings?Can you easily play back recordings?What is quality of device playback?What is quality of device playback? Is it easy to use?Is it easy to use? Is it too big or small?Is it too big or small?……


Personal Recording DevicesPersonal Recording Devices

Digital dictaphonesDigital dictaphones iPodsiPodsPDAs (Palms, Smartphones)PDAs (Palms, Smartphones)

Many have good specificationsMany have good specificationsFile format options can be quite limitedFile format options can be quite limitedOften have serious limitations regarding Often have serious limitations regarding

microphone/recording level flexibilitymicrophone/recording level flexibility


DictaphonesDictaphones


Other options: iPodOther options: iPod


Personal Recording DevicesPersonal Recording Devices


““Professional” Grade DevicesProfessional” Grade Devices

Greater flexibility in all areasGreater flexibility in all areasMinimize concerns about digitization specsMinimize concerns about digitization specsTypically use a .wav (uncompressed) formatTypically use a .wav (uncompressed) formatLarger and sometimes bulkyLarger and sometimes bulkyCan be quite expensiveCan be quite expensiveGood values if you look at devices designed Good values if you look at devices designed

for the music industryfor the music industry


Professional DutyProfessional Duty

Marantz PMD660Marantz PMD660~ $500~ $500



Boss Micro BRBoss Micro BR~ $230~ $230

Don Finan’s SealDon Finan’s SealOf ApprovalOf Approval



M-Audio MicrotrackM-Audio Microtrack< $300< $300


A Significant Disadvantage of A Significant Disadvantage of Recording with Portable DevicesRecording with Portable Devices

↑↑ ↑↑ Housekeeping dutiesHousekeeping dutiesSound recording file managementSound recording file managementNaming files so you know what is in themNaming files so you know what is in themMoving files from device or portable media to Moving files from device or portable media to

a more permanent archive (PC, CD)a more permanent archive (PC, CD)Finding software to replay the files you’ve Finding software to replay the files you’ve

acquiredacquired


PC Based RecordingPC Based Recording


Free (yes, free) software for Free (yes, free) software for recording/analyzing high quality speech recording/analyzing high quality speech

signalssignalsSpeech ToolSpeech ToolSFSWin (UCL Phonetics Lab)SFSWin (UCL Phonetics Lab)AlvinAlvinWavesurferWavesurferPraatPraatAudacityAudacity


Issues with PC recordingIssues with PC recording

Not all PC sound cards are identicalNot all PC sound cards are identicalVast majority work perfectly wellVast majority work perfectly wellOccasional problems includeOccasional problems include

Noise or staticNoise or staticShifts in recording baseline (does not affect Shifts in recording baseline (does not affect

how it sound)how it sound)

Documents

Copyright Tasko & Finan 2008 Instrumentation for “Dummies” Supporting Clinical Practice With Simple, Low-Cost Technology Stephen Tasko Ph.D. CCC-SLP Western