Chapter 9 Sound and the Ears Pg 287 Flashcards
Sound waves
Waves of pressure changes in air caused by the vibrations of a source
Cycle
Repeating segment of air pressure changes
*in a sound wave
Inverse square law
Falloff in sound energy with distance
*Energy of sound decreases in proportion to the square of the distance from the source
Three physical dimensions and perceptual dimensions
- Frequency=pitch
- Amplitude=loudness
- Waveform=timbre (sound quality)
Periodic sound waves
waves in which the cycles of compression and rarefaction repeat in a regular, or periodic fashion- opposed to aperiodic sound waves
Pure tone
Sound wave in which air pressure changes over time according to a mathematical formula called a sine wave, or sinusoid
Frequency
*Physical dimension of sound that is related to the perceptual dimension of pitch; expressed in hertz, the number of cycles per second of a periodic sound wave
Pitch
Perceptual dimension of sound that corresponds to the physical dimension of frequency; the perceived highness/lowness of sound
Hertz (Hz)
number of cycles per second of sound wave; the physical unit used to measure frequency
*Unimpaired hearing young adults- 20 to 20,000 Hz
Amplitude
The difference between the maximum and minimum sound pressure in a sound wave; the physical dimension of sound that is related to the perceptual dimension of loudness
Loudness
perceptual dimension of sound that is related to the physical dimension of amplitude; how intense/quiet a sound seems
*Peak amplitude: largest peak-to-trough difference
Decibels (dB)
Physical unit used to measure sound amplitude; logarithmically related to sound pressure measured in micropascals
- dB SPL= 20 log (p/p0)
- p is the measured sound pressure in micropascals (uPa)
- p0 is an internationally agreed-upon reference sound pressure of 20 uPa
- Just noticeable difference in intensity of sound= 1dB
- Physical sound pressure of less than 20 uPa are inaudible
Audibility curve
a curve showing the minimum amplitude at which sounds can be detected at each frequency
- The audibility threshold at the lower and higher frequencies that people can hear is much greater than it is at frequencies near the middle, around 500-5,000 Hz
- Auditory sensitivity is maximal in this middle range which happens to be the range of frequencies present in most human speech sounds
Equal loudness contour
A curve showing the amplitude of tones at different frequencies that sound about equally loud
*Our hearing is best for frequencies between 500-5,000 Hz
Unit of loudness
Phon
*Numerically equal to the amplitude of a 1,000 Hz tone- a 1,000 Hz tone at 10dB SPL has a loudness of 10 phons
Fourier analysis
mathematical procedure for decomposing a complex waveform into a collection of sine waves with various frequencies and amplitudes
Fourier spectrum
depiction of the amplitudes at all frequencies that make up a complex waveform
*Full array of its component frequencies with their specific amplitudes
Fundamental frequency
frequency of the lowest-frequency component of a complex waveform; determines the perceived pitch of the sound
Harmonic
component frequency of a complex waveform that is an integer multiple of the fundamental frequency; the first harmonic is the fundamental frequency; the second harmonic is twice the fundamental frequency, and so on.
Overtones
second and higher harmonics
- Second and higher harmonics are integer multiples of the fundamental frequency in many periodic sounds
- Complex periodic sounds’ qualify of their sound depends on the frequency and amplitude of their fundamental frequency and of each overtone
Timbre
difference in sound quality between two sounds with the same pitch and loudness; for complex periodic sounds, timbre is mainly due to differences in the relative amplitudes of the sounds’ overtones; the perceptual dimension of sound that is related to the physical dimension of waveform
- Low amplitude overtones contribute less to timbre
- Such differences in the relative amplitudes of harmonics are what give each sound its distinctive timbre
Pinna
outermost portion of ear; like a funnel and consists of fat and cartilage with various random-looking folds and ridges in it
*Modify the incoming sound in a way that contributes to sound localization
Auditory canal
narrow channel that funnels sound waves gathered by the pinna onto the tympanic membrane and that amplifies certain frequencies in those waves
*Amplifies frequencies in the range of 2,000-5,000 Hz, which contributes to the high sensitivity to those frequencies