Formulae!

Question 1

Frequency (in cycles per second)

Answer 1

1/periodic time

1/T

Question 2

Sound intensity

Answer 2

Sound power(P)/4πr^2

Question 3

Threshold of hearing

Threshold of pain

Answer 3

Hearing = 10^-12W/m^2

Pain = 10W/m^2

Question 4

Calculate dB

Answer 4

10*log10(sound intensity level measured/sound intensity level reference)

NB. bel scale is the same but log10 rather than 10*log10

Question 5

Calculate dBu

Answer 5

20*log10(sound pressure level measured/sound pressure level reference)
Our ref voltage for dBu is always 0.775V

Question 6

Calculate dBV

Answer 6

20*log10(sound pressure level measured/sound pressure level reference)
Ref voltage always 1V for dBV

Question 7

Calculate axial room modes

Answer 7

f= c/2L (double distance between 2 walls or wavelength)
f=c/λ

Complex version
f= (c/2)(sq root)(p/L)^2+(q/B)^2+(r/H)^2

Question 8

Bit rate calculation

Answer 8

Sampling rate x resolution x no. Of channels =bit rate

Question 9

Calculation for inverse square law

Answer 9

I (watts per metre square)=w / 4pie r^2

Question 10

Equation for wavelength

Answer 10

λ=c/f

Wavelength = speed of sound/frequency