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Published on November 28, 2007

Some of the questions are very basic but still need explaining to many car-buyers.

 Why is surround sound equipped with a "time delay"?

There are useful effects that can be created through the use of short time delays. The time difference between when the listener hears the direct sound and when the

reflection is heard is referred to as the delay time.

This depends on the distances between the listener, the sound source and the reflecting surface, with greater distances resulting in longer delay times. The delay time can be calculated by considering that sound travels in air at speeds of milliseconds, which are dependent largely on frequency types - low, mid, high and "signal phase".

Some loudspeakers are designed with delay time and phase shifts that neutralise distortion. In a surround-sound system, delay time plays a vital role in creating artificial surround-sound fields.

 

What makes sound recording come alive?

You may wonder why some auto CD players deliver better recorded music than others. This is often simply because the best sound engineers employ two separate microphones that duplicate the distance between the two front speakers in most cars.

 

What are ambience and reverberation?

Associated with rooms are the natural acoustic phenomena we call "reverberation" and "ambience". Reverberation and ambience consist of many repetitions of the original sound spaced so closely in time that no single repetition is distinctly audible. Concert halls are frequently evaluated on the basis of their reverberation time, that is, the time that it takes for a sound to decay away to inaudibility. If the reverb time is too long, the room can make speech difficult to understand; too short a reverb time will make a room sound dry and lifeless.

In the recording studio it is frequently desirable to add reverberation to recorded tracks. This can be done through some sort of artificial reverberation unit. The acoustic reverb chamber consists of an isolated room equipped with a loudspeaker and a microphone.

The microphone is used to pick up the reverberation in the chamber and is normally placed away from the loudspeaker to minimise the pick up of direct sound. The signal from the microphone is then amplified and returned to the control room where it is mixed with the playback signal so as to add just the desired amount of reverberation.

 

What is Matrix?

Dolby Surround/Pro Logic is based on basic matrix technology. When a Dolby Surround soundtrack is created, four channels of sound are matrix-encoded into an ordinary stereo (two-channel) soundtrack by using phase-shift techniques. A Pro Logic decoder/processor unfolds the sound into the original 4.0 surround - left and right, centre, and a single limited frequency-range mono rear channel - while systems lacking the decoder play back the audio as

standard stereo. All Dolby Digital decoders incorporate a digitally implemented Dolby Surround Pro Logic decoder for digital stereo signals that carry matrix-encoded Dolby Surround.

By Wijit Boonchoo

The Nation

Ultimate in Luxury

The Luxury LS 460 is a wonderfully comfaortable car fitted with all mod cons, althoough not necessarily the most fun vehicle to drive.