TechTalk
What is Frequency Response?
Frequency response is the measure of a sound
card's ability to handle music without changing the relative
loudness of sounds of various pitches. Errors in frequency
response is generally thought to be the most audible form of
Linear Distortion.
Frequency Response is a means of characterizing one form of Linear Distortion.
Frequency response is specified by the combination of three or four numbers. Two of the numbers specify a range of frequencies; and the third, or other two numbers specify a tolerance. The wider the range of frequencies for a given tolerance, the less Linear Distortion the card has. An ideal sound card would have a specification of at least 20-20kHz +0, -0.1 dB. Such a card would be unambigiously free of audible difficulties due to less-than-ideal frequency response.
The human ear is very sensitive to frequency response errors over the range from 500 to 8 kHz, as shown in the graoh "Level Match Criteria", shown below. In this range, response varitions as narrow as 1/3 octave, whose height or depth is no more than 1 dB, can be heard as a change in sonic balance between different sounds. Regions of raised or depressed response that cover a wider range are easier to hear. While not shown in the graph, narrow dips are generally thought to be less audible than narrow peaks.
Audibility of peaks and dips depends on the program material and the quality of other components in the system.. If the program material does not contain frequencies that are affected by such peaks and dips as exist, then the peaks and dips will have very little audible consequence. If other components in the system have significant frequency response variations, then smaller variations in the more accurate components may be harder to hear.
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