Choosing your Speakers: the Perception of Frequencies

To understand a little better the acoustic qualities of the speakers, it is useful to know how the ear works. It must first put it back in its place: on the head. The head and the whole body are sensitive to the vibrations of the air. By having enough level, we perceive all the frequencies between 0 and 40 kHz approximately. The head has an important role in the spatialization: the micro-movements which it constantly carries out unconsciously allow him to reconstruct the depth. Headphone perception, which is often more accurate because it is isolated from external noise, is very different from a spatial point of view.

Frequencies between 0 and 16 Hz are not sounds but vibrations. In cinema or home cinema, they reinforce the realism of certain scenes by reproducing the sub-harmonics present in reality (explosion, wind, percussion). It takes a modest enough level to perceive them ... only by the body, because the ear does not perceive them. Those with frequencies between 5 and 25 Hz interest will turn to home-theater vibrators that require a special installation but produce spectacular effects.

For audible frequencies, traditionally between 20 and 20,000 Hz, the sensitivity of the ear is strongly dependent on the intensity. The response is linear - that is, as sensitive in a bass, midrange, and treble - as from a level of 90 dB up to 110 dB. The level of 110 dB is only bearable for a few minutes ... hearing loss occurring beyond.

Below this sound level, the ear strongly favors the mediums. Thus, to find exactly the same perception in concert, it should listen to the same level of sound as in the room.

As for the pure frequencies, the human ear only really perceives them between 30 and 12,000 Hz. The zone between 12,000 and 17,000 Hz does not contain notes but harmonics that are decisive for the finesse of the timbres. Above 17,000 Hz, you can not hear anything directly unless you have a very high level of hearing sensitivity. People with tired ears (nightclubs, city life, musicians, DJs) often have hearing loss from 10,000 Hz.

What is the interest of a super tweeter?

The area beyond 20 000 Hz is very interesting: it is perceived directly by the skull. The fact of having a Hi-Fi playback amounting much beyond 20 kHz does not mean that the musical signal contains a lot. There is nothing to record in these frequencies. This allows, on the other hand, to significantly reduce the phase distortions in high frequency and that the ear is very sensitive. This is decisive for the spatial coherence of acoustic instruments, ie their placement - both in width and depth - and their size (a piano is larger than a violin).

The reverberations in the room are also very sensitive. So do not disregard loudspeaker and electronic systems (SA-CD for example): they are not addressed to bats ... it is a real progress for the high- fidelity in stereo, as in multi-channel.