anatomy quiz 2

phase

• exact position of a point within a wave cycle

• measured in degrees

• repeating wave = full circle motion

radian

• the amount of angle that would make its arc equal to the length to the radius

• 2pi radians = 360 degrees = one rotation

• pi radians = 180 degrees

• degrees to radians: multiply by pi over 180

phase difference$\theta=2\pi f\Delta t$

• difference in their positions within a cycle

amplitude

• maximum change in pressure

• magnitude of a vibration

• determines intensity of sound

• measured in pressure or dB

root mean square

the absolute average displacement at many points in time

benefits of RMS amplitude

• represents effective energy of sound

• correlates better with perceived loudness

• standard quantity used in SPL measurements

wavelength

• distance air molecules travels during one cycle (measured in meters)

• wavelength = c / f

• wavelength and frequency have an inverse relationship

• speed of sound: 343 m/s

wavelength and diffraction

• diffraction: bending of sound wave

• when sound travels through a smaller hole in object, the hole acts as a new sound source (sound waves radiate out of hole)

• smaller hole = more bend

• when wavelength is bigger than object, it will bend around

head shadow effect

• cut off frequency for diffraction is 1800 hz

• when frequency is high, head casts a shadow where the sound waves do not reach

doppler effect

frequency changes relative to where the source and listener are

time domain

displays waveforms of acoustic signal, graphing amplitude against time

frequency domain

displays how signal’s energy is distributed across various frequencies

line spectrum / continuous spectrum

describe how energy of a sound is distributed across frequencies

• line: shows individual frequencies

• continuous: used when there are too many frequencies represented

fast fourier transform spectrogram

computer application to obtain spectral analysis

waveform rise + fall envelopes

• puretones turn off/on suddenly, creating “popping” sound at start/end of signal, so amplitude increases and decreases

• plateau = full amplitude

octaves

frequency interval where the upper frequency is twice the lower frequency

ex) 250, 500, 1000, 2000

octave band

range of frequencies whose upper limit is twice its lower limit, and the center frequency is the geometric mean of the lower/upper frequencies

bandwidth

Measured from 3-dB Down Point / Half-Power Point

beats

Two pure tones of equal intensity but slightly different frequency combine, the combined tone will have an amplitude onset that grows to a maximum and then dies down to zero

the ear’s jobs

• Impedance Matching

• transduction

• transfer function