Decibels Flashcards
intensity is measured in ___ which is 1/10 of a ___
dB
Bel
a decibel is named after
Alexander Graham Bell
unit of intensity most commonly used is the
dB
dynamic range
difference between softest sound and loudest sound a human can hear
threshold of hearing
power: 1 x 10^-12 watt/m2
pressure: 20 uPa of .0002 dyne/cm2
threshold of pain
max amount to damage ossicles
power: 1x10^12 watt/m2
pressure: 200,000,000 uPa
decibel features
uses ratio
uses logarithm
nonlinear scale
various reference levels
dB IL
intensity level
watts/m2
electronics
10^-12
dB SPL
sound pressure level
noise levels
20 uPa
dB HL
hearing level
audiometers and audiograms
audiometric zero = 0 dB HL
dB SL
sensation level
20 above threshold
speech recognition testing
ratios mean
in relation to itself
audiometric zero
average pressure needed at each frequency
sensation level
presentation level - patient’s threshold
if the speech presentation level is 75 dB HL and the patient’s speech threshold is 30 dB HL what is the sensation level?
75 - 30 = 45
if the patient’s threshold is 50 dB HL and the presentation level should be 30 dB SL, what should the presentation level be in HL?
50 + 30 = 80
relationship between power and pressure
power = pressure 2
Power reference
dBIL = 10log
power output / power reference
Pressure reference
dBSPL = 20 log (power output / power reference)
rules: doubling
IL: 3
SPL: 6
rules: factor of 10
IL: 10
SPL: 20
70 dB SPL + 70 dB SPL
76 dB
just adding 6 because there are 2 speakers at 70
if the total SPL of two speakers is 140 dB, what is the SPL of each speaker?
140 - 6 = 134 dB
inverse square law
every time we double we subtract 6
every time we half we add 6
If Jimmy is sitting four feet from the teacher and receiving the teacher’s voice at 66 dB SPL and Jenna is sitting 8 feet from the teacher, what SPL is Jenna receiving the teacher’s voice at?
66 - 6 = 60 dB SPL
when sound intensity doubles the sound intensity level increases by
3
when sound pressure doubles, the sound pressure level increases by
6
when the sound intensity increases by a factor of 10, the sound intensity increases by
10
when the sound pressure increases by a factor of 10, the sound pressure increases by
20
every doubling of the distance from the sound source in a free field situation, the sound intensity will diminish by
6
