Perception of sound: Volume and perception of frequency, distorsion, Masking

Leggi questa pagina in Italiano Lire cette page en Franšais
CDROM Multimedia Audio Course Enjoying this Course?
Download the full version!

2.5.1. Volume and perception of frequency

The same sound is perceived as being more acute if the volume is considerably increased. The reasons for this phenomenon are still not completely clear.



2.5.2. Distortion

This phenomenon is fully described in the pertaining section [Distorter ] . For now it will suffice to highlight that distortion comes about when a signal gets saturated thus generating a whole set of new high frequencies.

To have a short glimpse of a distorted sound we report here two sounds: a plain guitar line and the same line after distortion has been applied:

Plain guitar line [Track 14]

Perception of sound - Plain guitar line[Track 14]

Distorted guitar line [Track 15]

Perception of sound - Distorted guitar line[Track 15]



2.5.3. Masking

A frequency with a high amplitude can mask nearby frequencies that have lower amplitudes. This happens because frequencies that are close to each other are picked up by hair-cells that belong to the same critical band. This characteristic is widely exploited to create digital audio data compression algorithms such as MP3 and ATRAC (used in MiniDisc systems [The MiniDisc ] ).