lec 2 Flashcards
why do we need logarithmic scales for measuring sound?
because our perception of loudness is non-linear; thus, using a logarithmic scale (like decibels) allows us to express a wide range of sound intensities in a more manageable and perceptually relevant format.
T or F: 0 decibels = silence
false – 0 decibels = below what humans hear
what is the range of sound pressures we normally encounter?
0.00002 to 20 Pa
diff bw intensity vs loudness?
- intensity: physical magnitude of sound energy (decibels).
- loudness: perceptual magnitude of sound energy (phons).
relative INTENSITY in dB is __ times the log of an intensity ratio.
relative PRESSURE in dB SPL is __ times the log of a pressure ratio.
- 10
- 20
what does log 10 mean?
- to what power must 10 be raised to produce a given number
- example: log10 of 100 = 2 because 10 to the power of 2 = 100
what do you do if you’re given:
20 log 10 (10^1)
- 20 x 1 = 20 dB SPL
what do you do if you’re given:
20 log 10 (2) [no exponent]
- press “log 10 of 2” on calculator (= 0.3)
- 20 x 0.3 = 6 dB SPL
what is the inverse distance law?
- the sound intensity at double the distance will have an intensity level that is decreased by a factor of 4 (and a surface area that increases by a factor of 4).
- I = 1/d^2 * Isource (formula will be provided, just know this is for inverse distance law)
in perception, the equivalent of the fundamental frequency (first harmonic) is ___
pitch!
how many semitones are in one octave?
12
T or F: people perceive a diff bw 200 and 400 Hz equal to a diff bw 2000 and 4000 Hz
true
for complex waveforms, each sinusoid is referred to as a ___
harmonic
Si = asin(bx+c)
in this formula, what do a, b, and c stand for?
- a = amplitude
- b = frequency
- c = phase
using Fourier Transform, we can go from waveform to spectrum.
what is the y and x axis of a spectrum? what about of a waveform?
- SPECTRUM: y = amplitude/intensity, x = frequency
- WAVEFORM: y = amplitude/intensity, x = time
