Amplitude Reference for Sound Synthesis


This page provides a table of amplitudes for note lists. When working with amplitudes the relevant unit of measurement is the decibel.

Table of Amplitudes

This table is based on the following premises.

To use this graph, determine the maximum number of simultaneous notes in your note list, then use the row of the table with the smallest voice count that equals or exceeds your maximum.

Voicesfff   ff   f   mf   mp   p   pp   ppp

Table 1: Amplitudes by voice count with zero-to-peak maximum 32767.

Frequency-Dependent Amplitudes

Pyschoacoustic research indicates that sensitivity to changes in amplitude vary with frequency according to the “equal-loudness contours” derived through experiment by Fletcher and Munson. A graph of these contours is presented in Wikipedia. Roughly summarizing, sensitivity at the low range of hearing (around 20 Hz.) ranges from 90 to 130 decibels. This region gradually widens while shifting downwards until around 3,500 Hz. where sensitivity ranges from -10 to 100 decibels. From that point the region narrows, shifting back upwards. At the upper limit of hearing (around 15,000 Hz.), sensitivity ranges from 10 to 110 decibels.

The catch is that equal-loudness contours were probably derived using sine tones, while the loudness of a complex tone with a low fundamental has more to do with the strength of the tone's harmonics in the more sensitive frequency regions. My recommendation therefore is to use the values given in Table 1 for your initial realization, then adjust amplitudes “by ear” to obtain the most favorable mix of highs and lows. If a low-fundamental voice speaks badly, you should consider using a waveform with stronger mid-range harmonics.

© Charles Ames Page created: 2013-02-20 Last updated: 2017-08-15