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Speech Science
02 Physics of Sound- Intensity
| Term | Definition |
|---|---|
| Sound INTENSITY | The sound pressure of a sound wave is a function of the force with which the object is put into vibration |
| force | the degree to which the air molecules surrounding the vibrating object are compressed |
| Frequency only changed by | mass |
| Intensity changed by | force |
| sound pressure is determined by | amplitude of the sound wave (higher the wave higher the sound pressure) |
| 2 Important Features of the dB Scale | -not an absolute scale . it is a relative scale, that compares one sound to another. -it is a logarithmic scale |
| 2 Ways to measure sound intensity | Direct - sound intensity level Indirect - sound pressure level |
| Formula for calculating decibels | dB SPL= 20 log (pressure of signal/20 microPas) |
| The characteristic of a log | The whole number |
| The mantissa of a log | The decimal portion |
| A tone is presented at a sound pressure of 500 uPa. What is the dB SPL? | dB SPL= 20 log 500 uPa /20 uPa = 20 log(25) = 27.958 dB SPL = 28 dB SPL |
| A tone is presented at a sound pressure of 6420 uPa. What is the dB SPL? | dB SPL = 20 log 6420 uPa /20 uPa = 20 log(321) = 20 (2.5065) = 50.13 dB SPL = 50 dB SPL |
| A tone is presented at a sound pressure of 940 uPa. What is the dB SPL? | dB SPL = 20 log 940 uPa /20 uPa = 20 log(47) = 20 log(4.70X101) = 20 (1.6721) = 33.442 dB SPL = 33 dB SPL |
| 2 tones are presented. Tone A produces 100 uPa. Tone B produces 50 uPa. Tone A is how many more dB than Tone B? | relative dB = 20 log 100 uPa /50 Pa = 20 log(2.0) = 20 log(2.0X100) = 20 (0.3010) = 6.02 dB Tone A is 6 dB greater than Tone B |
| 2 tones are presented - Tone A produces 2970 uPa. Tone B produces 150 uPa. Tone A is how many more dB than Tone B? | Relative dB = 20 log 2970 uPa /150 Pa = 20 log(19.8) = 20 log(1.98X101) = 20 (1.2967) = 25.934 dB -Tone A is 26 dB greater than Tone B |
Created by:
aramos139