Speech Technologies Fundamentals of AcousticsFundamentals of
Acoustics1.Sound and noise2.Sound and Noise Level measure3.Sound
Propagation4.Harmonic Plane Waves5.Pipes and Cavities: Acoustic
CircuitsSpeech TechnologiesSpeech Technologies Fundamentals of
Acoustics Definitions:AcousticGeneration, transmission, and
reception of energy in the form of vibrational waves in
matter.Sound ...... Dual Nature1. Vibrations transmitted through an
elastic solid or a liquid or gas. Physical phenomenon 2. The
sensation stimulated in the organs of hearing by such vibrations in
the air or other medium. perception Noise ...... Nonpleasant sound
(subjective)Fundamentals of Acoustics: Sound and NoiseSpeech
Technologies Fundamentals of AcousticsFundamentals of Acoustics:
Sound Level MeasureThe ear responds to pressure variationEffective
values (Root Mean Square)201lim ( )Tef iTP p t dtT=N/m2 =
PascalLimits:Limit of hearing ..... 20Pat 1 kHzLimit of pain
..........200 P at 1 kHzSound Pressure Level1020logefSPLrefPLP=Pref
= 20 PSound Power Level1010logWrefWLW=Wref = 10-12 WSpeech
Technologies Fundamentals of AcousticsSound Intensity (Acoustic
Intensity)Average rate of flow of energy through a unit area normal
to the direction of propagation (directional magnitude )[I] =
W/m2It is important because of:1.In the free space it is related to
the radiated power .In spherical waves2.In a point of the space it
has a fixed relation with the pressure.2( )4rWI rr =Intensity
Level1010logrefIILI=Iref = 10-12 W/m2Fundamentals of Acoustics:
Sound Level Measure2pIc =Speech Technologies Fundamentals of
AcousticsFundamentals of Acoustics: Sound Level MeasureSpeech
Technologies Fundamentals of AcousticsBlock Diagram of a
SonometermicrophonePreampli
fierOverloadDetectorWeightingnetworksFiltersAmplifierRMSDetector
DisplayWeighting networksFundamentals of Acoustics: Sound Level
MeasureSpeech Technologies Fundamentals of AcousticsEffects
produced by the noiseFrom minor to greater importance: Nervousness
and anxiety Interruption of the dream and the consequent lack of
concentration and irritability Interference in the spoken
communication Temporary loss of hearing with gradual recovery of
the same (brief exhibition at high levels of noise) Permanent loss
of hearing (exhibitions prolonged at high levels of noise or very
intense impulsive noises) Fundamentals of Acoustics: Sound Level
MeasureSpeech Technologies Fundamentals of AcousticsFundamentals of
acoustics: Noise Level MeasureStatistical MeasuresLA10 : dB(A) that
are exceed during 10% of the time LA50 : dB(A) that are exceed
during 50% of the timeLA90 : dB(A) that are exceed during 90% of
the timeLA10 is a peak levelLA90 is a background levelEquivalent
continuous sound level LeqThe steady-state sound that has the same
A-weighted level as that of the time-varying sound averaged in
energy over the specified time interval1011011010logiNLiieqNiitLt==
= Speech Technologies Fundamentals of AcousticsLeq over 8
hours:Personal daytime noise exposition< 85 dBACommunity noise
exampleFundamentals of acoustics: Noise Level MeasureSpeech
Technologies Fundamentals of AcousticsCommunity noise example
(cont.)Fundamentals of acoustics: Noise Level MeasureSpeech
Technologies Fundamentals of AcousticsCommunity noise example
(cont.)< 45 dBANo reactions45
