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In Reply to: Amp wattage question posted by valnar on June 10, 2004 at 13:32:56:
A 3db increase is twice the power, but not twice as loud. The ear is non-linear. Physiologists have devised a scale of loudness, which rank-orders sound from soft to loud on units of sones. The physical quantity measured is the sound pressure level. One thousand Hz is used as a reference frequency (where the ear is most sensitive), at a sound pressure level of 40 db above the threshold of hearing (0.0002 microbar). This level is refered to as 1 sone. Doubling the loudness is equal to 2 sones. The result was that for the ear to percieve a doubling in loudness, it takes a 10db change in sound pressure. So, it would take 10 times the amplifier power to be percieved as twice as loud, assuming the loudspeakers could handle to increase of 10db. So, you are right. doubling your power from 100 to 200 watts wont make much of a diffference. Long live horn loudspeakers!!
Follow Ups:
All's well in what you say except that the human ear does not have its highest sensitivity at 1KHz. That frequency was chosen as a reference (0dB) by Bell Labs before they did their population testing many decades ago. The maximum sensitivity is in the range of 3000-3500Hz and is due to the resonant characteristics of the external auditory meatus (outer ear canal) which is the acoustical equivalent of a stopped tube. As a result, the auditory threshhold in that range is about -6 to -10dB referred to 1KHz.
Oh no, someone was actually paying attention! You are correct, depending on the loudness level being used. At 40db (re 0.0002ubar), the Fletcher-Munson curves have 1kHz at almost the same sensitivity as the 3-4kHz region (within 1 db). These were the curves I used for reference. However, other studies give different sensitivity curves. The curves derived by Churcher and King show the greatest sensitivity (at 40db) at 2.5kHz, being about 2db greater than at 1kHz. The curves derived by Robinson and Dadson (free field) show the greatest variation, showing the greatest sensitivity at about 4kHz, and being about 8db more sensitive (again, at a 40 db level). Overall, all of the curves show the same general trends, and these were the basis for the equal loudness contours.
Thanks for keeping me honest!
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