How Often Should Audiometers Be Calibrated?

how often should audiometers be calibrated

Whether for occupational health or a private medical clinic, hearing testing equipment needs to be calibrated regularly. Called a Biological Calibration, these routine checks ensure that an audiometer is functioning correctly and conforming to ANSI standards.

Age, daily wear and tear, moisture and improper handling can impact the performance of an audiometer. This is why yearly calibration is recommended by manufacturers and many governing bodies.

Calibration Schedule

Audiometers are very precise electronic devices that are used to test hearing. They are regulated by the American National Standards Institute and require a high level of accuracy to produce accurate results. As such, they must be checked and calibrated on a regular basis. Having the correct calibrations allows you to perform accurate testing and comply with OSHA’s hearing conservation requirements. There are two types of calibrations: subjective and objective. Subjective calibration involves using a person with known hearing levels to test the equipment and determine if the output matches the correct values. This should be done on a regular basis, at least twice per year.

Objective calibration is a more in-depth check that uses an acoustic calibration system. This is performed at least once a year, but should be done more frequently if the audiometer shows unusual variations in output. These measurements are used to compare the acoustic output of the device to that specified by ANSI and ensure that the hearing threshold dial is set at the proper value.

In addition to checking for acoustic consistency, an objective calibration should also be used to test the audiometer’s transducers. A calibration system such as G4 LD Utility Software is able to test the sound pressure levels and vibratory force of the audiometer’s transducers. This is important because it can detect a problem with the sound pressure and vibration of the transducers, which could be causing inaccurate results.

Acoustical calibration can be done by either sending the audiometer to a lab or by having an expert come to your facility and use an acoustic calibration system. These systems can also test for other acoustic parameters such as frequency accuracy, harmonic distortion and attenuator linearity.

If you’re looking for a calibration service that will provide the most accurate and reliable results, contact your local e3 Diagnostics office. Our team of NASED certified technicians can calibrate virtually any type of audiometer. Contact us today to schedule an appointment! Inaccurate results from uncalibrated equipment can lead to a missed diagnosis, unnecessary treatment and even more damage to your patient’s ears.

Calibration Procedure

Performing a routine check on an audiometer is essential to ensuring that the device continues to function properly and adhere to ANSI standards. Known as a “Biological Calibration,” this test is conducted on an individual with known hearing levels and ensures that the audiometer is functioning correctly. Typically, the examiner tests their own or an assistant’s hearing at several frequencies (e.g., 1000 and 4000 Hz) to verify that the device is producing accurate results.

This calibration may be performed manually or with a dedicated acoustical calibrator. In the past, it was common for an acoustic calibration technician to visit a workplace and perform this type of exhaustive calibration. While this approach is still a viable option, today’s computerized audiometers often offer easy-to-use software that allows a more objective form of a functional check to be conducted in-house by the examiner.

When the Biological Calibration is complete, the examiner must also conduct a test that checks the overall functionality of the audiometer. This may include a basic listening check to verify that the tone sounds as expected, or an evaluation of any accessories and their condition. The ability to record these quick verification tasks and associated documentation can help a facility remain compliant with OSHA’s hearing testing requirements.

Modern computerized audiometers offer a variety of features that allow for daily verification tasks and the associated recording of those activities. These options can help an examiner quickly identify any issues with their audiometer and ensure it is functioning properly before conducting any testing.

For example, the aurical I and aurical II test boxes both have a menu setting that can be used to perform a simple aural calibration. Using this menu the audiometer is set to present a known signal (e.g., 94 dB SPL at 1kHz) to the artificial ear simulator or 2cc coupler (different adaptors for the coupler are required depending on the specific transducer). A sound level meter is connected to the microphone to measure the acoustic signal. When this value matches the setting on the audiometer the aural calibration is complete.

Calibration Report

The test results produced by an audiometer are only accurate if the audiometer itself is correctly calibrated. Calibration is a process that checks the accuracy of an audiometer by testing it on an individual with known hearing levels to ensure that the results produced are consistent. It involves running a simplified audiogram on the same person at regular intervals (at least every year) and ensuring that the hearing threshold levels recorded are accurate. A Biological Calibration typically includes testing the audiometer on the operator or an assistant at a minimum of two test frequencies per ear, although it is recommended to test all available hearing frequencies for consistency.

Traditionally, a Biological Calibration was conducted by sending the audiometer to a calibration laboratory or using a technician with a National Bureau of Standards 9A coupler, a laboratory sound level meter and a set of octave band filters. This method of acoustic calibration was often time consuming, expensive and disruptive to the day-to-day operation of a hearing center.

SHOEBOX Audiometry offers a convenient solution that eliminates the need for an external calibration lab or onsite technician. Rather than simply comparing the output of an audiometer to a standard, our patented Biological Verification system tests the acoustic calibration of the headset and its transducers (airway headphones, bone vibrator or insert-earphone) separately from the audiometer. This allows for the sharing of transducers between audiometers, reducing maintenance costs and downtime due to waiting for equipment to be re-calibrated or for a technician to visit your site.

Our patented system automatically performs a Biological Calibration every time the audiometer is turned on, checking that the output of each frequency has not changed significantly since the last annual calibration. This data is then compared to the original test result file for that patient. This creates a record of every test result since the audiometer was calibrated and provides an easy reference for future comparisons.

Inaccurate test results can lead to a misdiagnosis, unnecessary treatment or even permanent damage to the patient’s hearing. Keeping your audiometers regularly calibrated reduces the risk of inaccurate results and keeps you compliant with OSHA’s safety regulations.

Calibration Requirements

Inaccurate audiometer results can lead to a missed diagnosis, improper treatment, or even worsening of hearing loss. Regular calibration helps to prevent this and ensure that test results are valid. This is why both manufacturers and governing agencies recommend that a functional check of the audiometer should be conducted before every use.

The functional check can be a simple procedure that tests the audiometer by using a subject with known hearing thresholds and ensuring that the test results are consistent. This is also referred to as a biological calibration. Ideally, this should be done on a regular basis with the same person so that any variation in results is due to a change in equipment rather than a difference in hearing level. The test should be performed on a minimum of two frequencies between 500 and 4000 Hz.

Acoustical calibration is more complex and involves measuring the signal transmitted by an audiometer transducer in a coupler. Ideally this will be an artificial mastoid but may be a plastic or metal tube that is attached to the transducer. The coupler should be a 2cc (different adaptors are needed for different audiometer transducers) and it is important to disengage the air pipe from the 2cc coupler so that it is not damaged by accidental changes in pressure. The acoustic calibration should be conducted before each use and the results recorded.

Objective calibration of the audiometer is less frequently required but can be necessary if an acoustic or biological calibration indicates that the device is not functioning properly. An objective calibration is typically conducted by a certified e3 technician. This includes testing the audiometer on a person with known hearing levels and comparing the test results to the original specifications of the device as determined by the manufacturer. The objective calibration should be done on a regular basis and the test results should be within 10 dB of each other.

It is important to note that an audiometer must be calibrated for a wide range of frequencies in order to meet ANSI specifications. This is why it is important to select a calibration system that can test both high and low frequency signals. It is also important to select a calibration system that can be used with the type of sound level meter you will use in your practice. In addition, it is recommended that you consult your CAOHC Course Director or Professional Supervisor to discuss the appropriate calibration system for your specific environment.