Comparison of ANSI 2003 and ANSI 2009

This chart describes the differences between the 2003 and 2009 versions of the ANSI S3.22 hearing aid standard. Please also see our ANSI 96 – ANSI 03 comparison.



AGC aids should have their compression set to have minimum effect for all tests except for i/o and attack & release measurements. For those tests, the compression should be set to have maximum effect. Tests for AGC aids are not required in the standard in 2009. Suggested AGC aid tests are moved to the annex.
No definitions for compression or expansion of hearing aids. New definitions for compression and expansion as used in hearing aids, including the definitions of ratios.
All tests assume the use of pure tone test signals. A new requirement clause was added that in addition to pure tones, also allows the use of a noise signal for response tests if the it results in a gain response that tracks within 1 dB of the response obtained with the use of a pure tone within the pass band of the hearing aid. The FONIX composite signal is such a noise test signal.
Response tests are always measured in SPL with pure tone signals. When using pure tones, the measurement of a response can be in either SPL or gain. When using a noise signal, gain must be used.
Input SPL is defined for pure tone test signal. Input SPL for a pure tone signal is the same as before. Input SPL for a noise signal is limited to the bandwidth of from 200 to 5000 Hz.
Resolution of pure tone measurement specified. Analysis resolution of both pure tone and noise signals is specified.



  • Measurements made using 2003 standard meet requirements of 2009 standard, although not as efficiently.
  • The 2009 standard does not directly specify performing AGC hearing aid tests.
  • A noise signal may often be used in making response measurements.