Digital-Recordings Audio-CD Hearing Test

Digital-Recordings Audio-CD Hearing Test Disc

Digital Recordings of Canada have developed this compact disc that offers an easy and inexpensive method for detecting hearing loss early, allowing you to take preventive and corrective action.

Why? Because many activities subjects you to factors that can damage your hearing. These include excessive sounds from machinery, concerts, sound systems, personal stereos, bars / clubs, power tools, cars / boats; certain chemicals and even some medications.

Why should you be concerned? Because good hearing is important in everyday life, at work and at home. Good hearing keeps you safe when crossing the street or hiking in the bush. It allows you to communicate effectively with family, friends and colleagues. And it brings joy -- the sound of children laughing, music, nature etc. Therefore, it makes good sense to protect it. In some cases you can use ear protection. But since this is not always possible, or often regarded as unnecessary, there is another way to make sure your hearing stays in top shape.

"Digital Recordings' new CD the "AUDIO-CD" is a brilliant step forward ..."AUDIO-CD" is extraordinary and a most ingenious solution to making universal hearing testing cheap, reliable and effective....It makes the testing of hearing a simple home project which can be to the benefit of many people who suffer from partial hearing loss due to noise in the workplace or very loud music during their recreation. Digital Recordings is to be congratulated on taking advantage of modern technology in this ingenious way." Prof.Hugh Jones, H.W. Jones and Assoc., England

How is AUDIO-CD used for hearing testing?

AUDIO-CD provides anyone - for the first time ever - with an easy-to-use, self-administered hearing test right in the comfort of your home. The test is performed over a range of 24 frequencies - from 20 Hz, the lowest frequency humans can hear, to 20,000 Hz, the highest frequency humans can hear. All you need to perform the test is a CD player and a set of headphones or earphones.

How is hearing ability tested with AUDIO-CD?

Very easily! Sitting in a quiet room with headphones on you:

• calibrate the volume level in the headphones using the SCT (Special Calibration Tone); (The Special Calibration Tone included on the AUDIO-CD allows for volume calibration with ± 3 dB accuracy.);
• then assess the left ear by listening to test tones and recording the passage of time before each tone becomes audible (use the CD's timer to track the elapsed time);
• once all the tones are listened to turn the headphones around and repeat on the right ear.
• as the last step, the noted times are charted either by hand on the graph included in the AUDIO-CD booklet.

The graph below shows a sample chart of hearing test results. This chart is referred to as an audiogram. The "x"s indicate the left ear results, the "o"s indicate the right ear results. The grey line indicates the "ideal" results, which are the same for both ears.

 

How are hearing test results interpreted? The time (measured in seconds) that passes before the test tone is heard represents the intensity (measured in dB) of the tone at the point the tone is heard. Therefore, if it takes 10 seconds for the tone to be heard, the intensity of the tone at this point is 10 dB. This intensity is referred to as the "hearing threshold" for the tone. The purpose of one's hearing test is to find hearing thresholds for all of the test tones, chart them and then compare the charted results against the "ideal" hearing thresholds. An upward deviation of more than 10 dB from an "ideal" threshold indicates a hearing loss. The severity of a hearing loss can be determined based on the provided table. Any concerns with the hearing test results should be brought to the attention of an audiologist or acoustician.

over 70 dB Severe 55 - 69 dB Moderately Severe 40 - 54 dB Moderate 25 - 39 dB Mild 10 - 24 dB Slight Use this table for determining the severity of hearing loss.

 

How can hearing testing with AUDIO-CD help prevent hearing loss?

Permanent hearing loss, often referred to as Permanent Threshold Shift (PTS), can be caused by exposure to excessive sounds, loud music, certain chemicals and some medications. The sad fact is that, once damaged, hearing never gets better. Continued exposure to factors that cause hearing loss will make matters worse. Degradation is gradual. There is usually no pain or other alarming symptoms. Often hearing loss goes unnoticed until it starts interfering with verbal communication. At this point, damage to hearing is already significant.

A regular check of hearing ability (once every 6 months, for example), is the only truly effective method for identifying the early signs of hearing loss. This allows you to take preventive or corrective steps while damage to hearing is still in the early stages. The first audiogram should be used as a reference point and all consecutive audiograms should be compared against it. The series of audiograms will help to uncover any downward trends in one's hearing ability and identify the factors causing hearing loss.

AUDIO-CD is also ideal for determining temporary hearing loss, often referred to as Temporary Threshold Shift (TTS). This type of hearing loss usually disappears within 16 to 18 hours after prolonged exposure to moderate levels of sounds, chemicals or medications. A series of episodes of temporary hearing loss, with insufficient time for recovery between exposure, will eventually cause permanent hearing loss. Therefore, it is important to understand their causes. AUDIO-CD is often the only possible or practical solution for detecting temporary hearing loss. It allows you to test hearing ability right after exposure to sources of damage. To determine the presence and to assess the magnitude of temporary hearing loss, the test results should be compared against the reference audiogram.

Who benefits the most from using AUDIO-CD for hearing testing?

AUDIO-CD is of benefit to both general public and health care professionals. In particular it is of great use to

• those whose job depends on good hearing (audio engineers, sound engineers, musicians, doctors, pilots, radio operators, telephone operators, drivers, divers);
• those who are exposed to excessive noise at work (stone cutters, machine operators, mechanics, construction workers, carpenters, farmers)
• members of the armed forces and police departments (for in-the-field testing)
• hunters and gun users
• anyone exposed to loud sounds, music, chemicals, medications, radiation
• researchers in the fields of acoustics, psycho acoustics, audiology, psychology, speech pathology, biology (especially for testing of hearing in animals)
• as well as all those who value their hearing.

What do others think about AUDIO-CD?

The following testimonial is typical of those who have used AUDIO-CD: " The quality of the stimuli (i.e. the test tone) is very good and the procedure to find HTs (i.e. Hearing Thresholds) is very clever (my colleague - Dr. Brad McPherson - used the word 'ingenious'). Clearly, given the limitations of testing someone's hearing on his/her own hi-fi at home, it would have been very difficult to find an easier procedure to use." Dr.Valter Ciocca, University of Hong Kong, Hong Kong

Technical

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. 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.