Download presentation

Presentation is loading. Please wait.

Published byWendy Countess Modified over 2 years ago

2
Hearing and Deafness 2. Ear as a frequency analyzer Chris Darwin

3
Frequency: 100-Hz Sine Wave Time (s) 00.05 1.0 0 Waveform Amplitude against time Spectrum Amplitude against frequency 1 100 Hz amp frequency

4
Frequency: 500-Hz Sine Wave Waveform Amplitude against time Spectrum Amplitude against frequency 1 500 amp frequency 1 100 amp frequency500 Time (s) 0 0.05 1.0 0

5
Amplitude: 500-Hz Sine Wave Spectrum Amplitude against frequency 1 500 amp frequency 1 100 amp frequency500 Time (s) 0 0.05 0 Time (s) 0 0.05 0

6
Phase: 500-Hz Sine Wave The amplitude spectrum does not show phase 1 500 amp frequency 1 100 amp frequency500 sine cosine

7
Phase Locking of Inner Hair Cells Auditory nerve connected to inner hair cell tends to fire at the same phase of the stimulating waveform.

8
Phase-locking

9
adding sine waves 1 amp frequency 1 amp frequency 1 amp frequency 1 amp frequency Spectrum of Sum

10
100-Hz fundamental Complex Wave Waveform Amplitude against time Spectrum Amplitude against frequency Time (s) 00.05 -1.7 5.0 0 1 500 amp frequency 1 100 amp frequency500

11
Adding nine sine waves Frequency Time Frequency Time Spectrogram5s

12
The linear vs log scales Linear equal distances represent equal differences 0 100 200300 400 500 100 200 400 800 1600 3200 -1 0 1 2 3 4 Log equal distances represent equal ratios e.g. Piano keyboard frequencies Octave = doubling of frequency basilar membrane has log repn of frequency

13
deciBel (dB) scale Sound A is x dB more intense than sound B when: x = 10*log10 (energy of A / energy of B) or x = 20*log10 (amp of A / amp of B) So if A is 20 watts and B is 10 watts x = 10*log10 (20/10) = 10*0.3 = 3dB You can usually just hear a difference of 1dB (jnd)

14
Bandpass filtering (narrow) Time (s) 00.05 -1.7 5.0 0 1 500 amp frequency 1 100 amp frequency500 Time (s) 0 0.05 0 1 50 0 amp frequency 1 100 amp frequency500

15
Bandpass filtering (wide) Time (s) 00.05 -1.7 5.0 0 1 500 amp frequency 1 100 amp frequency500 1 amp frequency 1 100 amp frequency500

16
Beats 1 amp frequency 1 100 amp frequency500 Repetition rate is the difference in frequency between the two sine-wave components 1/3 second505 - 500 = 5 Hz

17
Beats 1 amp frequency 1 100 amp frequency500 Repetition rate is the difference in frequency between the two sine-wave components 1/100th second500 - 400 = 100 Hz 400

18
Reponse of basilar membrane to sine waves Each point on the membrane acts like bandpass filter tuned to a different frequency: high freq at base, low at apex. Each point vibrates at frequency of pure tone (-> phase locking)

19
Excitation patterns (envelope of excitation) Basilar membrane excitation pattern is like a spectrum

20
Auditory filter bandwidth (ERB)

21
Excitation pattern of complex tone on bm

22
Measurement of auditory bandwidth with band-limited noise Broadband Noise 1000 Hz 2000 Hz frequency 250 Hz Amadeus

23
A gardening analogy

25
Auditory bandwidth Noise bandwidth Detection mechanism Tone Noise

26
Wider auditory filter

27
Psychophysical tuning curves Bandwidth

28
Auditory tuning curves Healthy ear Inner hair-cell damage

29
Outer-hair cell damage

30
Human auditory bandwidth At 1 kHz the bandwidth is about 130 Hz; at 5 kHz the bandwidth is about 650 Hz. BW = freq / 8 roughly

31
Normal auditory non-linearities Normal loudness growth (follows Weber’s Law, which is logarithmic, not linear) Combination tones Two-tone suppression Oto-acoustic emissions

32
Combinations Tones (Tartini tones) 1 amp frequency 1 1000 amp frequency 1200 800

33
Two-tone suppression

34
Conductive vs Sensori-neural deafness Becomes linear, so No combination tones Or two-tone suppression Mostly a combination of OHC and IHC damage

35
Symptoms of SNHL Raised thresholds: helped by amplification Wider bandwidths: no help possible Recruitment (restricted dynamic range): partly helped by automatic gain controls in modern digital aids Often accompanied by tinnitus

36
Normal vs Impaired Dynamic Range

Similar presentations

Presentation is loading. Please wait....

OK

Intensity of a Spherical Wave

Intensity of a Spherical Wave

© 2017 SlidePlayer.com Inc.

All rights reserved.

Ads by Google

Ppt on tsunami early warning system Ppt on types of computer Ppt on domains of earth Ppt on eid festival india Ppt on channels of distribution for a product Ppt on agriculture free download Ppt on human chromosomes genes Ppt on mergers and acquisition process Ppt on product advertising letter Ppt on solar system in hindi