Monday, December 18, 2006

Audibility - Decibles and Frequency

I am doing some research to help define a standard for the audible interactions of a handheld device. The sound is used to create a confirmation of an action, to remind the patient of an action they are or should perform or a warning that they need to take action. I have reviewed what similiar products are doing and also what normal everyday things sound like.
Here is a list from of the approx. decibel rating of common sounds from

30 Soft whisper
35 Noise may prevent the listener from falling asleep
40 Quiet office noise level
50 Quiet conversation
60 Average television volume, sewing machine, lively conversation
70 Busy traffic, noisy restaurant, alarms of medical equipment
80 Heavy city traffic, factory noise, alarm clock
90 Cocktail party, lawn mower
100 Pneumatic drill
120 Sandblasting, thunder
140 Jet airplane
180 Rocket launching pad

Above 110 decibels, hearing may become painful
Above 120 decibels is considered deafening
Above 135 decibels, hearing will become extremely painful and hearing loss may result if exposure is prolonged
Above 180 decibels, hearing loss is almost certain with any exposure

It is important to understand that sound is measured in both decibles and frequency. Decibles(dB) is the strength of the sound, while frequency(Hz) is the cycles per second of the sound. Each person will respond to the combinations of dBa + Hz with the perception of some being louder than others. You can test your hearing at The University of New South Wales - Music Accoustics site.