Fletcher Munson CurvesTriphosphate wrote:Ah you're absolutely right. But above post is also right that distortion adds harmonics. But yes... A tone at 1000hz for example is still 1000hz wether it's -10db or 0 db.-[2]DAY_- wrote:i think its the inverse of this.... as in, when you raise the pitch to higher frequencies, your brain interprets it as louder even though its the same amplitude.Triphosphate wrote:I could be wrong but I think as things get louder the brain sometimes interprets them as being higher pitch, a psychoaccoustic phenomena. It's a negligible change though, and I think higher frequencies are subject to it more so than lower. But you won't really 'hear' 10hz so much as feel it anyways.
Anyway frequency is how fast the cone moves, and amplitude is how far it moves.
changing Frequency will alter the perceived loudness of said frequency at a consistent decibel output. This ties into frequency masking.
Where the perceived loudness of a specific frequency will 'mask' that of a similar frequency in accordance with the diagram above. Note the unbalanced nature of the bell curves. A frequency has a higher propensity to mask frequencies of a similar decibel higher in frequency than itself at a rate of decreasing linearity the further away from the masking frequency the masked frequency resides, as stated, with a high propensity to higher frequencies than lower. Mixing engineers and M.E.'s use this rule of psychoacoustics often in their work as a way of masking unwanted content of sounds that don't add constructively to the mix.
Note that the perceived loudness will perform frequency masking, which depending on the area of the frequency spectrum in question and the amplitude in question, may be quite removed from the objective (true) loudness of the frequency in respect to how much said frequency should be masking that of another frequency.
A live piano for example, as each note has such a complex harmonic nature will have a certain timbre created by the various forms of frequency masking happening at different areas of the pitch register. Trying to retain that delicate balance of a realistic sounding piano in the recording studio to be played back in a digital medium, one has to take into consideration perceived loudness and frequency masking as turning up the amplitude on the mixing desk (to place the piano in the mix) will alter the perceived loudness of the bass register, which in turn will mask frequencies in the lower mids/mids that were adding important elements to the timbral relationship of the overall sound. One would have to carefully apply appropriate EQ to counteract this effect.
lots of links in there... 
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