PSYCHOACOUSTICSThreshold or LimenMinimum Audibility Curve--PowerPoint PresentationAuditory ResponseAreaDifferential SensitivityWeber’s Law--A Theory of human differential sensitivityLoudness/PitchMeasuring Loudness:Equal Loudness Contours: The Phon LinesSlide 11PITCH:Slide 13PITCH UNITSComplex SignalsSlide 16MASKINGMasking Varieties:Slide 19Critical Bands: FletcherFrequency ResolutionGood Frequency Resolution Allows you to:Brief Sounds: Temporal IntegrationTemporal Aspects: TEMPORAL INTEGRATIONBinaural Hearing: Some TermsLOCALIZATION & LATERALIZATIONSound LocalizationLOCALIZATION CUES:Masking Level Difference (MLD)Masking Level Difference (MLD) (cont’d)PSYCHOACOUSTICS•A branch of psychophysicsThe study of the relation between: •the physical aspects of sound and •the psychological experience of soundThreshold or Limen•Absolute Threshold -- lowest value of stimulus which can be detected•Difference Threshold -- smallest detectable change in a stimulus•These 2 Thresholds were the primary questions in CLASSICAL PSYCHOPHYSICSThresholdsMinimum Audibility Curve--•Plot of threshold of detection (in dB SPL) as a function of frequency•Lowest thresholds in 1 to 4 kHz regionThresholdsThe Auditory Response AreaThresholdsAuditory ResponseArea•Range of useable hearing-- from threshold of detection to threshold of feeling/pain•Also called the DYNAMIC RANGE OF HEARINGThresholdsDifferential Sensitivity•Detecting changes in a stimulus•(e.g., how small a change in frequency can you detect)•Measured as the jnd - just noticeable differenceDiff. Sensitivity//Weber’s LawWeber’s Law--A Theory of human differential sensitivity•  S/S = k•Size of jnd = constant fraction of the stimulus you start with•It’s easier to detect small changes in a stimulus if it had a small value to begin with.Diff. Sensitivity//Weber’s LawLoudness/Pitch•Loudness--psychological experience most directly related to sound pressure/intensity•Pitch--psychological experience most directly related to frequencyLoudness/PitchMeasuring Loudness:•Matching Procedure: listeners match loudness of tones at various frequencies to 1000 Hz tone -- yields unit of loudness called the PHONLoudness/PitchEqual Loudness Contours: The Phon LinesLoudness/PitchMeasuring Loudness:•Estimation or Scaling Procedure: listeners rate tones for loudness -- yields unit called the SONE •1 sone = loudness of a sound with a loudness level of 40 phons. •2 sones are twice as loud as 1 sone. •Loudness in Sones Doubles Every 10 dB Loudness/PitchPITCH:•Place Code•Periodicity Pitch•Missing Fundamental Phenomenon Loudness/PitchLoudness/PitchPITCH UNITS•mel scale--The psychophysical unit of pitch•semitone - used in music; describes the ratio (16/15) in frequency between sounds. (Also used for the half step in the standard chromatic scale)Loudness/PitchComplex Signals•Sounds with energy at more than one frequency•Timbre: Sense of voice or identity: conveyed by harmonics and timing patterns.MASKINGThe interference with the perception of one sound produced by the presence of a second soundMaskingMasking Varieties:•EARS: Ipsilateral = Masker & Signal in same ear vs. Contralateral = M in one, S in other•TIMING: Simultaneous = M & S on at same time vs. Forward = M precedes S vs. Backward = M follows SMaskingMaskingCritical Bands: FletcherMaskingFrequency Resolution•The Critical Band reflects “internal filtering”--the ability to attend to a narrow range of frequencies•Remember the tuning curves from Bekesy’s dead ear and the healthy cochlea?•You need the healthy cochlea to have good frequency resolving powerGood Frequency Resolution Allows you to:•Listen to harmonic structure of complex signals•Detect Shifts in Frequency (esp. formant transitions)•Hear and Understand signals in noiseBrief Sounds: Temporal IntegrationTemporal IntegrationTemporal Aspects: TEMPORAL INTEGRATION •A certain amount of energy must be present for detection of a brief signal.•The process of summing energy over time is called integration and it is completed by 300 ms.•If the signal is shorter than 300 ms, then power must be increased for the signal to be detected. Temporal IntegrationBinaural Hearing: Some Terms•AZIMUTH-angle from straight ahead in horizontal plane.•Minimum Audible Amgle- jnd for azimuth.(smallest at 0 degrees, largest near 90 and 270 deg.)BinauralLOCALIZATION & LATERALIZATIONLOCALIZATION:•ability to determine location of a sound source in the sound field.LATERALIZATION:•perceived position of sound within your head for stimulation under headphones.BinauralSound LocalizationBinauralLOCALIZATION CUES: •INTERAURAL TIME DIFFERENCE works best at low freqs: up to 0.65 ms at 90 deg.•INTERAURAL INTENSITY DIFFERENCE works best at high freqs: where head shadow exists.•PRECEDENCE EFFECT people can tell which ear was stimulated first.BinauralMasking Level Difference (MLD)Masker and Signal in Each EarTest Threshold twice: >once with identical signals in each ear>once with 180 degrees out of phase R to LBinauralMasking Level Difference (MLD) (cont’d)•Signal is easier to detect with the interaural phase difference•Shift in threshold is about 12 to 15 dB at low frequencies.•Reflects processing in the auditory