Having your audiometers calibrated regularly is essential to ensure that test results comply with strict industry standards and the manufacturer’s specific guidelines. It’s also mandated by law in some countries.
This study found a high degree of variation in thresholds between different audiometers, far beyond the normal calibration tolerances.
Calibration Requirements
Like any other piece of medical equipment, hearing care professionals must properly maintain their audiometers to ensure it provides accurate test results for patients. Calibration is one of the ways to do this, and it is recommended that it be conducted on a regular basis (at least annually). This process consists of configuring the device to verify that it meets certain specifications. In some cases, the calibration process can even be required by governing bodies or manufacturers.
During the calibration process, an audiologist will use a sound source with known hearing levels to check that the audiometer is working correctly. The test results should produce a result within 10 dB of the actual hearing level.
The frequency of the calibration process depends on the type of audiometer and the procedure used to measure hearing. For example, air-conduction supra-aural headphones will require a calibration more often than acoustic insert earphones. Moreover, the sound pressure tolerances of each audiometer type are also different. Hence, the calibration of each device will need to be tailored to the specific requirements of each facility.
In addition, the quality of the acoustic transducers will also impact the performance of an audiometer. This is why it is important to use high-quality transducers that are acoustically calibrated for optimal performance. KIVERSAL has developed an innovative and patented calibration system that makes this easier than ever before. By separating the acoustic calibration of the transducers from the audiometer itself, it becomes possible to easily interchange the transducers among multiple audiometers of the same brand. This will cut down on maintenance costs, and eliminate the need to travel between clinics for calibration services.
Although further study is needed to identify the exact contribution of the acoustic calibration process and headphone placement to the test-retest variation seen by Byrne et al, it can be concluded that the issue is significant. This is particularly true since the study simulated clinical practice by testing the same subject on different devices that were not manufactured by the same company. The acoustic calibration of the individual meters was carried out in different laboratories, so there should be no expectation that these differences would be replicated between real clinics.
Calibration Methods
A well-calibrated audiometer is a crucial piece of equipment for a hearing clinic, since the resulting test results have implications for patients moving forward. They will likely receive medical intervention or recommendations for hearing aids based on the findings of their exam, so it is critical that those diagnoses are accurate and consistent across different clinics. In order to ensure consistency and accuracy, audiologist should regularly calibrate their equipment.
The calibration process involves a number of steps, including testing the SLM, SC, and ear simulator to trace their performance and provide correction factors. The frequency of the testing may vary depending on the audiometer and method chosen. In the past, calibration was often done in-house by a hearing professional, but as technology has improved, many audiometers now feature built-in calibration tools. However, it is still important to record the thresholds of a primary and alternate listener for each audiometer, in case any errors occur during the bio-cal procedure.
There are several different types of audiometers, but all of them use a similar approach to calibrating the SLM and ear simulator. The calibration process is conducted by comparing the output of the SLM to the target value, then adjusting the settings on the audiometer until the outputs match. In a previous study, Byrne et al found that the calibration process was affected by both temperature and aging of the SLM, which can cause a variation in the signal-to-noise ratio (SNR).
Audiometers are very precise electronic devices that are regulated by strict values set by the American National Standards Institute. These devices must also comply with the manufacturers’ specific references for hearing thresholds, so a failure to properly calibrate them could result in inaccurate test results. For this reason, governing bodies and manufacturers recommend annual calibration.
A calibration report is provided with each audiometer that is tested, and it is essential to keep this documentation in a secure location. When a new audiologist joins the team, they should take the time to review the documentation to understand how the audiometer should be used. They should also be familiar with the correct procedures for performing daily biological calibrations. This will ensure that the audiometer continues to produce reliable test results and conforms to ANSI requirements.
Calibration Tools
An audiometer’s calibration system is the key to ensuring your hearing tests are accurate. Many important decisions – both human and legal – are made based on the data produced by an audiometer, so accuracy is essential. That’s why GRAS offers a wide range of audiometer calibration systems to help you meet ISO 389 and achieve accuracy every time.
Audiometers are complex electronic instruments that use high-precision transducers, microphones, and a sound level meter to perform test results. These components are sensitive to daily wear and tear, moisture, and not-so-gentle handling, which is why the manufacturers and governing bodies recommend annual calibration of these devices.
It is recommended that all audiometers be checked and calibrated before each day’s use. This functional check is conducted by testing a person with known, stable thresholds and listening to the audiometer’s output to ensure it is free of distorted or unwanted sounds. If the output deviations are greater than 10 dB at any test frequency, an acoustic calibration is required.
An acoustic calibration is a more objective form of the functional check performed by evaluating an audiometer using the techniques described in Appendix E to ANSI S3.6. The calibration equipment needed includes a sound level meter and an acoustic coupler. A National Bureau of Standards 9A coupler is recommended for audiometry calibration.
Performing regular, comprehensive calibration of your audiometer can prevent costly errors, such as incorrect referrals and follow-up appointments. This can also help reduce the time spent by audiologists conducting a full set of test, which is a great benefit to your clients.
A fully-calibrated audiometer will produce consistent and comparable tone presentation throughout your clinic. This is important because your clients may be used to getting the same results in other clinics and assume that their audiometer is calibrated correctly. However, different audiometers can produce the same results differently due to variations in their internal tolerances.
If you are tired of stopping your business to perform an annual calibration on your audiometer, consider investing in a smart one. The KIVERSAL smart audiometer is a fast and convenient way to keep your clinic up and running while maintaining the required annual calibration. It combines the functionality of an audiometer with a digital signal processor, which allows you to quickly send the data as an email, link or fax without having to stop the procedure. You can even blackout confidential information, add comments and highlights and more with the built-in KIVERSAL tools.
Calibration Procedures
A calibrated audiometer is only useful if it produces accurate results. To ensure this, an audiologist will need to carry out quick verification tasks daily before conducting testing on a patient. There are a few ways to do this and each must be recorded in your clinic’s record-keeping system.
These verifications will check the audiometer’s function as well as its output and should be performed by any examiner who is authorised to do so. These quick checks help to ensure that the test results produced comply with ANSI standards and those of the manufacturer of your equipment.
One such simple and quick test is the Biological Calibration hearing threshold check. This can be conducted by using a primary and at least two alternate human listeners. The primary and alternate are required to be of the same gender to avoid variations in the results. The tests should be conducted on a range of frequencies, including those that would be used with patients. These tests should be repeated to make sure that the results remain unchanged.
If the Biological Calibration is not producing accurate results, you must perform an acoustic calibration to confirm that the output of your audiometer conforms to ANSI specifications. This will involve checking the acoustic calibration of the audiometer’s transducers, using a sound level meter to measure their output. If the acoustic calibration of the transducers is found to be inaccurate, you must then conduct an exhaustive calibration on your audiometer.
Having a good quality audiometer is vital for conducting a comprehensive occupational hearing test, however the use of an incorrectly calibrated audiometer can lead to erroneous and unreliable test results. A poorly calibrated audiometer can result in a significant difference between the test results of different examiners and can therefore lead to bias and misdiagnosis of hearing loss. This can have legal and professional implications and should be avoided at all costs.
To reduce the risk of an inaccurate or faulty audiometer calibration, you can purchase a GRAS acoustic calibration system which will provide a fast and efficient means of checking your audiometer’s output. The GRAS systems are easy to set up and operate, and can be upgraded as your audiometer needs change. A range of accessories is also available, which can be connected to the audiometer to provide a variety of functions such as the ability to test with headphones of different sizes and brands.