We generally characterize sounds by their pitch, loudness, and quality. We refer to the quality of a sound as its timbre. Timbre (tam-burr) is the color or character of a sound. We hear timbre because our ears fuse together and experience as a single sound the multiple frequencies that most sounds contain. More simply, timbre is the sound characteristic that allows our ears to distinguish between sounds that have the same pitch and loudness.
Timbre is mostly determined by a sound’s harmonic content it its dynamic characteristics such as vibrato and the attack-delay envelope of the sound. (Georgia State University: http://hyperphysics.phy-astr.gsu.edu/hbase/sound/timbre.html)
I had not intended to take such a long break between posts, but a two week vacation and a few other things delayed this update. The subject of today’s post is how we perceive loudness in digital audio.
In audio software such as Audacity the relative strength of an audio signal is usually measured in decibels. In many of these programs 0 dB is the highest peak the application can handle, and if you normalize an audio file, the sound peak will be set at -0.X dB. It is important to know that decibel ratios only loosely correlate to the way our ears perceive significant changes in volume. If we increase a sound by 3 dB the relative volume is doubled, but to our ears it will not sound like the volume has been doubled. If we want the sound file to sound twice as loud we may have to increase the volume level by 20 or 30 dB.