what do we hear? sound is a compression wave - it only “looks” like a wave if we plot air...
TRANSCRIPT
![Page 1: What do we hear? Sound is a compression wave - it only “looks” like a wave if we plot air pressure against time time -> Air Pressure Period - amount of](https://reader035.vdocuments.net/reader035/viewer/2022070415/5697c0281a28abf838cd6d98/html5/thumbnails/1.jpg)
What do we hear?
• Sound is a compression wave - it only “looks” like a wave if we plot air pressure against time
time ->
Air Pressure
Period - amount of time for one cycle
Frequency = number of cycles per second (1/Period)
![Page 2: What do we hear? Sound is a compression wave - it only “looks” like a wave if we plot air pressure against time time -> Air Pressure Period - amount of](https://reader035.vdocuments.net/reader035/viewer/2022070415/5697c0281a28abf838cd6d98/html5/thumbnails/2.jpg)
Sensing Vibrations
• Inside the cochlea is the basilar membrane• Movement of the oval window causes ripples
on the basilar membrane
![Page 3: What do we hear? Sound is a compression wave - it only “looks” like a wave if we plot air pressure against time time -> Air Pressure Period - amount of](https://reader035.vdocuments.net/reader035/viewer/2022070415/5697c0281a28abf838cd6d98/html5/thumbnails/3.jpg)
Hearing• Detection • Loudness • Localization• Scene Analysis • Music• Speech
![Page 4: What do we hear? Sound is a compression wave - it only “looks” like a wave if we plot air pressure against time time -> Air Pressure Period - amount of](https://reader035.vdocuments.net/reader035/viewer/2022070415/5697c0281a28abf838cd6d98/html5/thumbnails/4.jpg)
Detection and Loudness
• Sound level is measured in decibels (dB) - a measure of the amplitude of air pressure fluctuations
![Page 5: What do we hear? Sound is a compression wave - it only “looks” like a wave if we plot air pressure against time time -> Air Pressure Period - amount of](https://reader035.vdocuments.net/reader035/viewer/2022070415/5697c0281a28abf838cd6d98/html5/thumbnails/5.jpg)
Detection and Loudness
• Sound level is measured in decibels (dB) - a measure of the amplitude of air pressure fluctuations
• dB is a log scale - small increases in dB mean large increases in sound energy
![Page 6: What do we hear? Sound is a compression wave - it only “looks” like a wave if we plot air pressure against time time -> Air Pressure Period - amount of](https://reader035.vdocuments.net/reader035/viewer/2022070415/5697c0281a28abf838cd6d98/html5/thumbnails/6.jpg)
Detection and Loudness
• Sound level is measured in decibels (dB) - a measure of the amplitude of air pressure fluctuations
• dB is a log scale - small increases in dB mean large increases in sound energy
• We have a dynamic range that is a factor of 7.5 million!
![Page 7: What do we hear? Sound is a compression wave - it only “looks” like a wave if we plot air pressure against time time -> Air Pressure Period - amount of](https://reader035.vdocuments.net/reader035/viewer/2022070415/5697c0281a28abf838cd6d98/html5/thumbnails/7.jpg)
Detection and Loudness
• minimum sound level necessary to be heard is the detection threshold
![Page 8: What do we hear? Sound is a compression wave - it only “looks” like a wave if we plot air pressure against time time -> Air Pressure Period - amount of](https://reader035.vdocuments.net/reader035/viewer/2022070415/5697c0281a28abf838cd6d98/html5/thumbnails/8.jpg)
Detection and Loudness
• detection threshold depends on frequency of sound:
• very high and very low frequencies must have more energy (higher dB) to be heard
• greatest sensitivity (lowest detection threshold) is between 1000 hz to 5000hz
![Page 9: What do we hear? Sound is a compression wave - it only “looks” like a wave if we plot air pressure against time time -> Air Pressure Period - amount of](https://reader035.vdocuments.net/reader035/viewer/2022070415/5697c0281a28abf838cd6d98/html5/thumbnails/9.jpg)
Detection and Loudness
• Detection can be compromised by a masking sound
• even masking sounds that are not simultaneous with the target can cause masking (forward and backward masking)
![Page 10: What do we hear? Sound is a compression wave - it only “looks” like a wave if we plot air pressure against time time -> Air Pressure Period - amount of](https://reader035.vdocuments.net/reader035/viewer/2022070415/5697c0281a28abf838cd6d98/html5/thumbnails/10.jpg)
Detection and Loudness
• Loudness is the subjective impression of sound level (and not identical to it!)
![Page 11: What do we hear? Sound is a compression wave - it only “looks” like a wave if we plot air pressure against time time -> Air Pressure Period - amount of](https://reader035.vdocuments.net/reader035/viewer/2022070415/5697c0281a28abf838cd6d98/html5/thumbnails/11.jpg)
Detection and Loudness
• For example, tones of different frequencies that are judged to be equally loud have different SPLs (dB)
![Page 12: What do we hear? Sound is a compression wave - it only “looks” like a wave if we plot air pressure against time time -> Air Pressure Period - amount of](https://reader035.vdocuments.net/reader035/viewer/2022070415/5697c0281a28abf838cd6d98/html5/thumbnails/12.jpg)
Detection and Loudness
• Hearing loss due to exposure to high-intensity sounds (greater than 100 dB) is frequency-specific and can last many hours
![Page 13: What do we hear? Sound is a compression wave - it only “looks” like a wave if we plot air pressure against time time -> Air Pressure Period - amount of](https://reader035.vdocuments.net/reader035/viewer/2022070415/5697c0281a28abf838cd6d98/html5/thumbnails/13.jpg)
Detection and Loudness
• Incidence of noise-related hearing loss is increasing dramatically• iPods and other “earbud” music players are thought to be partly
responsible• How loud is an iPod?
– maximum volume is approximate but is somewhere between 100 dB (hearing damage in about 2 hours) to 115 dB (hearing damage in about 15 minutes)
• Consequences: difficulty understanding speech, tinnitus, deafness • Your perception of loudness adapts so it’s hard to tell how loud your
iPod is - LOCK THE VOLUME ON YOUR iPOD!