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Technical Specifications

AUDIO-CD's technical specifications rival ANSI standards and specifications of the best clinical audiometers on the market today.

Signal generation digital synthesis (DFG-S software)
S/N (Signal-to-Noise ratio) 96 dB
Frequency response 20 Hz - 20,000 Hz +/- 0.0001 dB
Signal Frequencies [Hz]
(bold indicates "standard" audiometric frequencies)
20, 40, 60, 125, 250, 500, 750, 1k, 1.5k, 2k, 3k, 4k, 5k, 6k, 7k, 8k, 9k, 10k, 11k, 12k, 14k, 16k, 18k, 20k
SPL range 0 dB - 80 dB (in 1 dB steps)

How were the "ideal" hearing thresholds determined?

The hearing ability of a group of young children with no history of hearing loss was tested in an audio booth using AUDIO-CD and AKG-K270 headphones. An average hearing threshold was obtained for each of the test tones. The averaged values are the "ideal" hearing thresholds.

At this point the "ideal" hearing thresholds should be viewed as preliminary data. It is the hope of Digital Recordings that AUDIO-CD will be used to further refine them.

How accurately does AUDIO-CD test hearing ability?

The accuracy of the hearing test results depends on the quality of the headphones and the CD player, the noise level in the room at the time of the test, and the precision with which the volume level in the headphones was calibrated. The higher the quality of the headphones and the CD player, the quieter the room, and the more precise the calibration of the volume level in the headphones, the more accurate the test results will be.

AUDIO-CD contains SDS (special digital signal) for evaluating the CD player's suitability for the hearing test.

And, what about the quality of the AUDIO-CD recording? All test tones, the special calibration tone, and the special digital signal were synthesized digitally and are of very high quality.

The factors impacting on the accuracy of test results are less of a concern when the AUDIO-CD
is used for monitoring changes in hearing ability. In this case it is the change in the hearing threshold that matters and not its absolute value. However, to get an accurate picture of the trend in one's hearing ability, it is recommended that during all tests the same headphones be used, and that the calibrated volume in the headphones stays at the same level from test to test.

What if a more objective way of calibrating headphones is required?

For those who look for a more objective way of calibrating the volume level in headphones, Digital Recordings offers, at additional cost, an electronic volume calibrator (left) or a mechanical coupler to be used with a sound level meter. Two types of mechanical couplers are available; one for headphones (right) and one for earphones (middle). Digital Recordings also offers an inexpensive semi-professional coupler DR1-R. For more details on each of the products click here.

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