Precise measuring instrument

What Is – and How To Perform – a Biological Calibration

Audiology and ENT Clinics, Hearing Conservation, Hearing Services, Humanitarian

Audiometers are very precise electronic instruments used for testing human hearing.  They are regulated by ANSI/ASA S3.6-2010, which is the standard that provides the specifications and tolerances for such devices. To ensure that your audiometer continues to function accurately and conform to the standard, it is necessary for you to check and verify the audiometer routinely. Called a biological calibration or verification, these checks are performed to confirm that the system is free of any defects that might erroneously impact test results.

Look for Any Signs of Damage

A biological calibration is a subjective test that starts with a physical examination of the audiometer and all accessories. It is meant to look for any signs of damage to any piece of equipment or accessory – including transducers, ear cushions, plugs, and cords. Specifically, you should check the following:

  • For signs of wear or damage
  • That tones presented are coming through on the correct side
  • That the system has sufficient battery charge for your planned testing time
  • To ensure that transducer serial numbers align with the audiometer they will be used with
  • That no audible noise is emitting from the system

It is also best to ensure that all the connections between the portable audiometer equipment components are free from intermittencies and/or static and crackling. You can do so by applying pressure to any connection jack and moving the pressure around to see if you detect any issues.  This applies to any connector cables to or from the device.

Conduct A Simplified Audiogram

A Biological Calibration is also intended to check that any resulting output is accurate. This is done by conducting a simplified audiogram on an individual with known hearing levels, then ensuring no change in results. The operator may test themselves or an assistant and record hearing threshold levels at various frequencies. A minimum of two frequencies per ear is recommended (e.g. 1000 and 4000 Hz), but you can also choose to test all frequencies that would be used with patients.

Testing the same individual using the same device at regular intervals should produce results within 10 dB. This Biological Calibration can be used to ensure that the system is free of defects, is functioning properly, and continues to conform to the ANSI standard.

Create a Historical Record of All Biological Calibrations

When using SHOEBOX Audiometry, it is possible to create and store a historical record of all of the Biological Calibrations that have been performed on the device. Simply create a fictional patient – named, for example, Biological Calibration. Select this ‘patient’ every time you perform a check. With a baseline audiogram already saved for that patient, it is very easy to compare subsequent tests against the baseline to confirm that the system is working as expected. This is also useful for auditing and/or troubleshooting purposes, as it will be easy to find a tally of all the results from your biological verification activities.

Should you need to substitute the person who had been doing the biological verifications, add a new patient and change the name slightly – for example, Biological Verification2 – and create a new baseline with which to compare thresholds?

When Is It Time to Recalibrate?

The acceptable test-retest range is +/-10 dB for any frequency. In other words, should your tested threshold(s) be more than 10 dB different from the baseline, a recalibration or change of headset could be required.

If you have any questions about SHOEBOX and how to use it in your clinic, practice, or program, contact us and let us know how we can help.