Performing accurate hearing assessments depends on the functioning of equipment like audiometers. These devices are acoustically calibrated to ensure they meet the ANSI standard. This calibration involves testing a person with known air and bone conduction thresholds.
CAOHC course directors suggest a routine, preventative approach to calibrations. Ask your professional supervisor or audiometer supplier about electro-acoustic calibration services for mobile units.
1. Accuracy
The accuracy of audiometers is essential to ensure that hearing tests produce accurate results. Incorrect results can lead to misdiagnosis and inaccurate treatment plans for patients. For this reason, it is important to calibrate your audiometer regularly, preferably annually. This will help to ensure that it is functioning correctly and complies with the strict standards set by ANSI and the manufacturer.
Whether you have a traditional, conventional or smart audiometer, it is important to make sure that it is maintained in optimum working condition. The best way to do this is to invest in calibration services. This will not only help to avoid costly mistakes, but also allow you to run your business more efficiently and provide exceptional patient care.
Audiometers are designed to detect sound pressure levels and convert them into a representation of the patient’s hearing thresholds. Ideally, the test sounds are produced at a level that is neutral to hearing and will not cause any discomfort or pain to the patient. However, the noise levels of a room and the environment in which the test is performed can influence the accuracy of the measurements. It is therefore a good idea to perform an ambient testing test at the time of your annual and exhaustive calibration, or at any time that you notice significant changes in the internal sound booth environment such as greater truck traffic.
An acoustic calibration is an in-depth functional check of your audiometer, conducted using a sound level meter and octave-band filter set. The procedure is simple – place the earphone coupler over the microphone of the sound level meter and set its HTL dial to 70 dB. Measure the sound level of tones at each of the frequencies from 500 Hz through 6000 Hz and note each measurement on the sound level meter. The total deviation of the readings should not exceed 15 dB at any frequency.
In addition to acoustical calibration, an exhaustive calibration is a detailed, more in-depth analysis of your audiometer’s functionality, and may include adjustments according to ANSI specifications. Exhaustive calibrations should be carried out every year, or more often if the results show deviations of more than 10 dB.
2. Reliability
Audiometers are generally reliable, as long as they are used correctly and in a quiet environment. However, daily wear and tear, age, and not-so-gentle handling can all have a negative impact on the equipment’s reliability and affect test results. This is why many manufacturers and governing bodies require annual calibrations of audiometers.
An audiometer is a device used to evaluate hearing by testing for sound frequency and intensity. It consists of embedded hardware connected to a pair of headphones and a test subject feedback button, sometimes controlled by a standard PC. Some types of audiometers also incorporate bone vibrators to test conductive hearing mechanisms. Audiometers are usually certified to ISO 13485:2016 and IEC 60645-1:2017 standards to ensure that they meet specific requirements.
The functional operation of the audiometer must be checked each day prior to use by testing a person with known and stable hearing thresholds or a bio-acoustic simulator. The tester must also listen to the output of the audiometer to make sure it is free from distorted or unwanted sounds. Any deviations from the specified output levels of 10 decibels or more warrant an acoustic calibration of the audiometer.
An exhaustive calibration is performed annually, and it consists of a more in-depth analysis of the audiometer’s output specifications to determine whether or not there are any unusual variations. It is recommended that the exhaustive calibration be conducted by a trained and experienced technician in accordance with the American National Standards Specification for Audiometers, S3.6-1969.
During the acoustic calibration, all tones are presented for the shortest possible time in the order of octave frequencies from 250 to 8,000 Hz. The test participants are asked to rapidly press and release the response button as soon as they hear a tone in either ear. The audiologist can then compare the response times with the corresponding thresholds to verify that the audiometer is functioning properly.
The results of the acoustic and exhaustive calibration of the audiometer are documented in a Calibration Report, or Certificate of Conformity (COC), that is kept on file. The COC document is essential for maintaining the integrity of the test results, as it provides proof that the test equipment has been tested and complies with the necessary standards for audiometry.
3. Safety
An accurate audiometer is crucial in ensuring the safety of workers. In environments with machinery or emergency signals, hearing loss could cause miscommunication that leads to dangerous consequences. Regular hearing screenings are critical in identifying these issues and ensuring employees meet strict occupational health and safety standards. But, for these tests to yield reliable and accurate results, the equipment must be calibrated correctly. This means using a reliable test subject with standard hearing to compare their responses to the audiometer’s known calibration levels. A specialized device like the Tremetrics Oscar 6 can do just that, providing an official calibration check to ensure that your screenings align with OSHA’s requirements.
Performing an audiometric function check on the audiometer is required by OSHA before each hearing screening. This includes checking the attenuator’s slewing rate, confirming that it remains at each test frequency for 30 seconds, and examining that the output level for each frequency complies with ANSI or the older ASA/USASI standards. These checks can be simplified with the use of a specialized audiometer that performs both an official calibration and a mechanical function check. This helps to eliminate discrepancies between the meter’s output level and clinically expected thresholds.
In addition to conducting a functional check on the audiometer, it’s important to periodically inspect and clean the earpieces and jacks of your auditory screening equipment. These devices can collect earwax and dust that can negatively impact sound quality, so it’s important to keep them clean to maintain optimal performance.
Also, be sure to store your audiometer in a protective case or other safe location when not in use, so it isn’t exposed to environmental factors that can cause damage over time. Finally, if you’re using silicone tubes for your transducers, make sure they’re not discolored or damaged before reusing them. Additionally, make sure you’re always using the correct tube for your audiometer model.
If your workplace’s audiometers aren’t calibrated regularly, it could lead to inaccurate test results that can be costly for your business. Taking the time to ensure your audiometer is properly calibrated is well worth it in terms of creating a safer and more productive work environment for your employees.
4. Legality
A valid audiogram must adhere to specific OSHA hearing conservation program requirements. This includes an accurate test of all required frequencies and the ability to accurately measure ambient noise levels in the testing location to ensure presentation tones aren’t being obscured by higher ambient noise levels. A clinically validated automated testing platform can easily meet these requirements, making it easier to keep OSHA-required documentation practices consistent across locations.
To be legal, an audiogram must also include conversational voice and pure tone speech discrimination tests. This means employees must be able to distinguish their own voice from that of the tester, and that they can understand a variety of spoken words with ease. This requirement may require that workers are trained in proper test administration, as well as in using the equipment correctly.
Finally, the law requires that an audiogram must be obtained with equipment that is maintained, calibrated and checked by a licensed audiologist, otolaryngologist or physician. This also applies to a technician operating microprocessor-type audiometers.
Keeping audiometers in good working order prevents inaccurate measurements, safety issues and legal problems. In addition, it encourages employees to take a proactive approach to their own occupational health and wellness, as they are reminded that their personal sound protection is essential to their careers and overall hearing health. Bryan A. Liang is a professor of law at California Western School of Law and director of the Institute of Health Law Studies. His research focuses on the intersection of law, health care and public policy, including issues involving ethics, fraud and abuse, and patient safety.