Sound Quality Factor

What is It?

Many folks talk about the sound quality of various sound decoders in very subjective ways. Bruce wasn't satisfied with this. While the final quality of the sound is VERY dependent on the speaker system design, the better the sound quality from the decoder, the better the overall installation will sound.

The number of bits is important. But it doesn't tell the whole story.

The sampling rate is part of the mix, too. But by itself, it doesn't do the trick.

While driving back to Munds Park from the Tehachapi Loop, Bruce got the idea of a Sound Quality Factor rating for decoders. This SQF number is a relative rating of the sound quality that the decoder is capable of producing. This is the ability of the hardware to reproduce sound programmed into the decoder.

It does NOT comment on the quality of the basic recording.

It does NOT take into account amplifier power or the speaker system being driven.

SQF is a calculation, based on the number of bits of sound data and the sampling rate in KHz. What is really important is the relative values for different decoders. Use this as a yardstick.

The bigger the number, the higher the ability to reproduce sound quality.

The table below shows popular sound decoders and compares SQF for each. Since the highest frequency a digital system can reproduce is half of the sampling rate, that number is included, too. Bruce believes that 8 KHz is the minimum high frequency for decoders to provide good bell and whistle (horn) tone and he personally prefers 12 KHz. Human hearing extends as high as 15 to 20 KHz.

Manufacturer

Decoder Series

Bits

Sample Rate

Max frequency

SQF

Digitrax

SoundFX

8

11

5.5 KHz

88

ESU

LokSound

8

12

6 KHz

96

SoundTraxx

Tsunami

16

44

22 KHz

704

 

QSI has not provided Bit and Sample Rate data to be included in this table.

Copyright © Bruce F. Petrarca 2007 - 2017; All Rights Reserved