| A | B |
|---|
| Po = 20 microPascals | 20 log Po/Pr = 20 log 20/20 = 20 log 1 = 0 dB SPL |
| Po = 8 microPascals | 20 log Po/Pr = 20 log 8/20 = 20 log 0.4 = -7.96 dB SPL |
| formula to convert sound pressure to dB SPL | 20 log Po/Pr |
| formula to find frequency [Hz] given period | f = 1/Tsec |
| formula to find period given frequency | Tsec = 1/f |
| formula to find wavelength given pure tone frequency | wavelength (m) = c/f, c=331 m/sec |
| formula to find wavelength given f0 of periodic complex sound | wavelength (m) = c/f0, c=331 m/sec |
| unit for wavelength | meters, centimeters (any length unit) |
| unit for frequency | Hz (cycles per second) |
| unit for sound pressure | microPascals, Pascals |
| unit for period | seconds, milliseconds |
| to convert seconds to milliseconds | multiply by 1000 |
| to convert milliseconds to seconds | divide by 1000 |
| to convert meters to centimeters | multiply by 100 |
| to convert centimeters to meters | divide by 100 |
| signal to noise ratio | signal level (dB SPL) - noise level (dB SPL) |
| inverse square law | sound level drops by 6 dB each time distance from the sound source is doubled |
| 5th harmonic of periodic complex sound | 5 x f0 |
| two octaves above 200 Hz | 800 Hz |
| high pass noise (HPN) | noise composed of all frequencies ABOVE a cut-off frequency |
| low pass noise (LPN) | noise composed of all frequencies BELOW a cut-off frequency |
| cut-off frequency | frequency limit of noise (e.g., a LPN with a cut off of 1000 Hz will contain only frequencies below 1000 Hz) |
| broadband noise (BBN) | a noise composed of a wide range of frequencies |
| narrowband noise (NBN) | a noise composed of all frequencies in a limited range |
| bandpass noise (BPN) | a noise composed of all frequencies between two cut-off frequencies |
| white noise | broadband noise containing all frequencies at the same amplitude |
| amplitude spectrum | shows the frequency components of a sound at one point in time (also shows relative amplitude of the components) |
| waveform | shows the amplitude of the sound over time |
