When two tones are perceived simultaneously, other tones often appear, because of distortion effects in the ear. Relatively high intensity levels are required for combination tones to be heard, and strong differences exist between individuals as to how many are heard. If two sine tones are played at a sufficient intensity level, one high (x) and the other low (y), the combination tones usually heard are the difference tones, at frequencies equal to (x - y), (2y - x) and (3y - 2x). The summation tones of frequencies (x + y) and (2x + y) are seldom if ever heard, even when in the audible range, possibly because of masking effects. (Source - Barry Truax - Handbook for Acoustic Ecology CD-ROM Edition. Cambridge Street Publishing, 1999 - CSR-CDR 9901)

Lorsque deux hauteurs sont perçus simultanément, d'autres hauteurs apparaissent souvent et sont causées par un effet de distorsion produit par l'oreille. Pour apparaître, ce phénomène nécessite un niveau d'intensité relativement élevé. De plus, des différences de perception importantes existent entre des individus différents. Si deux hauteurs sinusoïdales sont jouées à un niveau d'intensité suffisant, un son aigu (x) et un son grave (y), la combinaison de hauteurs généralement perçue correspond à la différence des hauteurs à fréquences égales (x - y), (2y - x) et (3y - 2x). Les sommes des fréquences (x + y) et (2x + y) ne sont que rarement, voire jamais perçues, même dans un intervalle audible. La raison est probablement due aux effets de masque. (Source - Barry Truax - Handbook for Acoustic Ecology CD-ROM Edition. Cambridge Street Publishing, 1999 - CSR-CDR 9901)

Quando l'orecchio umano ascolta due suoni contemporaneamente, in alcune circostanze può accadere di ascoltare altri due suoni, che dipendono dal fenomeno di distorsione dell'orecchio. Perché il fenomeno si produca, occorre che l'intensità dei suoni sia elevata, ma varia anche in base alla sensibilità dell'orecchio delle varie persone. Se due suoni sinusoidali, uno acuto (x) e uno grave (y), sono suonati ad un livello di intensità sufficiente, la combinazione udita è il risultato della differenza delle altezze pari a (x - y), (2y - x) e (3y - 2x). La somma delle frequenze (x + y) e (2x + y) è udita raramente, anche se appartenente all'ambito udibile, probabilmente a causa degli effetti di mascheramento (Fonte - Barry Truax - Handbook for Acoustic Ecology CD-ROM Edition. Cambridge Street Publishing, 1999 - CSR-CDR 9901).

When two tones are perceived simultaneously, other tones often appear, because of distortion effects in the ear. Relatively high intensity levels are required for combination tones to be heard, and strong differences exist between individuals as to how many are heard. If two sine tones are played at a sufficient intensity level, one high (x) and the other low (y), the combination tones usually heard are the difference tones, at frequencies equal to (x - y), (2y - x) and (3y - 2x). The summation tones of frequencies (x + y) and (2x + y) are seldom if ever heard, even when in the audible range, possibly because of masking effects. (Source - Barry Truax - Handbook for Acoustic Ecology CD-ROM Edition. Cambridge Street Publishing, 1999 - CSR-CDR 9901)

Cuando dos sonidos son percibidos simultáneamente, otros tonos frecuentemente aparecen a causa de los efectos de distorsión del oído. Para poder escuchar los sonidos diferenciales (también llamados tonos combinacionales o de combinación) son necesarios niveles de intensidad relativamente altos, y existen grandes diferencias sobre el número que puede ser percibido de acuerdo con cada individuo. Si dos tonos sinusoidales son tocados con suficiente intensidad, uno agudo (x) y el otro grave (y), los tonos combinacionales usualmente oídos son los que corresponden a la diferencia entre ambos, en frecuencias iguales a (x - y), (2y - x) y (3y - 2x). Los tonos suma, de frecuencias (x + y) y (2x + y) son raramente oídos, aún cuando estén dentro del rango audible. Esto posiblemente sucede por efecto del enmascaramiento.

(Fuente: Barry Truax (1999). Handbook for Acoustic Ecology. CD-ROM. Cambridge Street Publishing. CSR-CDR 9901)