SOUND
What is sound?
Sound is a vibration of molecules in the air. Sometimes intense, sometimes weak, these vibrations can create long or short wavelengths.
A large amplitude vibration will yield a high sound pressure level while low amplitudes will create a lower level of sound pressure. The same goes for wavelengths: short wavelengths yield higher sound frequencies, while long wavelengths yield lower sound frequencies. These vibrations travelling through the air are captured by your ears which transform them into sound.
Sound intensity
Acoustic pressure is measured in decibels (dB SPL) but, for all sorts of reasons, sound thresholds are represented on a different scale: dB HL.
Most sounds range from 0 to 25 dB HL while conversation can reach up to 50 dB HL.
A place that is too noisy will cause discomfort and even pain. While this can occur at a lower level, it is estimated that 120 dB is the threshold pressure for discomfort. Between 120 and 140 dB, sound pressure becomes painful.
Degrees of hearing loss:
- Slight loss: 25 to 40 dB
- Moderate loss: 41 to 54 dB
- Severe to moderate loss: 55 to 70 dB
- Severe loss: 71 to 90 dB
- Profound loss: more than 90 dB
Frequency
Frequency is a concept that is often used when referring to sound. This reflects the pitch and is measured in Hertz (Hz), which corresponds to the number of vibrations per second captured by your ears. High pitched sounds are composed of many vibrations per second, while low pitched sounds have less. The human ear can capture sounds between 20 and 20,000 Hz.
