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3) Performance and Response

3.1 Unintended and Intended changes

The definitions and requirements for audio, sound and quality described in chapter 1 present two classes of processes in an audio system: those that unintentionally decrease the audio quality of the system (and with it the sound quality), and those that intentionally increase the sound quality of the system.

An ideal audio system will pass any signal in the audible range of the human auditory system in full, without limitation or unintentional change, offering fixed and variable processes that intentionally change the audio signal in order to increase the system’s sound quality. In real life however, audio systems always limit and unintentionally change signals within the audio universe - which means that the limitation and unintended changes can be heard by individuals listening to the system. By definition, limitation and unintended changes of audio signals decrease the sound quality because if such a limitation or change could be avoided, the product manufacturer / system designer would have done so. Also, if a limitation or unintended change would be found to increase the sound quality, we assume that the product manufacturer / system designer would redefine it as an intended change.

Intended changes posed to audio signals by a system’s processes by definition increase the sound quality - because if they would not increase the sound quality, the product or system designer would not have applied them in the system.

This arrangement seems logical, but it poses a philosophical problem: ‘Sound quality’ is a subjective parameter - every individual will assess sound quality differently. Therefore, the decision to designate a system process as intended or unintended change is subjective - different listeners might designate processes - eg. a signal path with a fixed EQ curve or a compression - differently: one listener might prefer the process, and the other might not.

To make the designation of processes in an audio system ‘semi-objective’, or at least properly defined, we propose to view the matter strictly from a manufacturer / system designer’s perspective, and define the decision method to designate system processes as unintended or intended change as follows:

audio system processes designated as unintended change
-all fixed processes that are listed by the product manufacturer / system designer without reference to a positive contribution to the product / system’s sound quality

-all fixed processes not mentioned in the product manufacturer / system designer’s promotion or specification sheets.

audio system processes designated as intended change
-all variable processes

-all fixed processes that are promoted by the product manufacturer / system designer in promotion or specification sheets as a positive contribution to the system’s sound quality

Of course individual listeners can disagree with the decisions made by product manufacturers and system designers, differing in their preferences for individual processes in the audio system. Even when preferences are averaged, audiences for different genres of music (eg. pop, classical, jazz) might have different average preferences for an audio system’s process. To accommodate these differences, there are two design philosophies that product manufacturers and system designers can apply: ‘natural sound’ and ‘coloured sound’. To define these philosophies, first the concept of system Performance and system Response is presented.

>3.2 Performance and Response

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