• New Terminology
• Measure AGC aids in RTG position
• More options to define AGC
• New Telecoil measures

DIRECTIONAL HEARING AID {3.14}

• A directional hearing aid is an instrument whose microphone output changes as a function of the direction from which sound waves arrive at the input.

 
• An anechoic environment, one in which sound vibrations are all but eliminated, is required for testing directional hearing aids according to the S3.22 standard.

SPECIAL PURPOSE HEARING AID {3.15}
 

• A special purpose hearing aid is an instrument whose effective bandwidth lies substantially outside the usual amplification range;

 
• specifically, where the full-on gain at any of the “HFA” frequencies (1000, 1600, and 2500 Hz) is more than 15 dB lower than the maximum full-on gain at any frequency.

 
• Examples are high-frequency- or low-frequency-emphasis instruments.

SPLITS {3.16}—

SPLITS is an abbreviation for SPL in an inductive tele-phone simulator. A coupler curve is run with the hearing aid in telecoil mode with the gain control at the reference-test position. The input is a magnetic field generated by a Telephone Magnetic Field Simulator.

HIGH-FREQUENCY AVERAGE SPLITS (HFA-SPLITS)—
 

The HFA-SPLITS value is the average of the decibel levels at 1000, 1600, and 2500 Hz taken from a SPLITS curve with the hearing-aid gain control at the reference-test position.
 

OUTPUT SOUND PRESSURE LEVEL—
The output sound pressure level (also called output level) is the SPL measured by the coupler microphone.

OUTPUT SOUND PRESSURE LEVEL FOR 90 dB INPUT SPL (OSPL90) {3.5}—
the OSPL90 is the output level of a hearing aid when the input level is 90 dB SPL and the gain control is full-on.

TELEPHONE MAGNETIC-FIELD SIMULATOR (TMFS) {3.20}—The TMFS
is a device used to produce a magnetic field that is consistent in both level and geometric shape. According to the standard, the current shall be equal to 6 milliamperes divided by the number of coil turns.

SETTING THE TRIMMERS OR PROGRAMMING

• In general, set all trimmers or programming to give the widest possible frequency response range, the maximum gain, and the maximum output.

 
• If it is not possible to achieve both the maximum output and the maximum gain, set the aid for the maximum output.

 
• An exception is an AGC instrument having compression controls {3.13}. Set the controls as indicated by the manufacturer. The manufacturer may designate the settings with a clear physical mark, as the end of the control rotation, or with programmable parameter values.

• It’s a good idea to check the accuracy of your leveling/testing system, from time-to-time, by running a leveled frequency response test without a hearing aid and coupler present.

 
• The result is the frequency response of the testing system, which should show the output level to be the same as the input level at every frequency within ± 1.5 dB between 200 and 20000 Hz and within ± 2.5 dB between 2000 and 5000 Hz.

ACTUAL TESTS
 

• NON AGC AID
• AGC AID

ANSI S3.22-1996 (revision of ANSI ’87) Specification of Hearing Aid Characteristics

Following graph taken from information in the Frye Electronics manual.  Additional information available from:  
        http://www.frye.com

 
 

SUMMARY OF TOLERANCES
 

The tolerances of the measurement equipment must be added to or subtracted from S3.22 tolerances, as appropriate. (Refer to Section {6.16} for further explanation).
 

TEST    TOLERANCE
 

• OSPL90    max Specified value + 3 dB

 
• OSPL90 (HFA or SPA)  Specified value ± 4 dB

 
• Full-on gain (HFA or SPA)  Specified value ± 5 dB

 
• Reference-test gain None  (information purposes only)

 
• Reference-test position Gain control must be within ± 1 dB of the target setting, such that the HFA (or SPA) output for a 60 dB-SPL: input is 17 dB below the OSPL90 HFA (or SPA), unless the full-on gain is already  lower

 
• Frequency response curve  Low band: specified curve ± 4 dB; high band:specified curve ± 6 dB;  curve may be shifted 10% left or right, and unlimited up or down

 
• Frequency range    None (info purposes only)

 
• Percent total harmonic distortion  Max is specified value + 3%

 
• Equivalent input noise (EIN) level  Max is highest specified value + 3 dB

 
• Battery current drain.  Max is highest specified value + 20%

 
• Input-output (I/O) characteristic  After normalizing at 70-dB-SPL input point, outputs for 50- and 90-dB-SPL inputs must be within ± 5 dB or specified values.

 
• Attack and release times   Specified value ± 5 ms or ±50%, whichever is larger

 
• HFA- or SPA-SPLITS:   Within ± 6 dB of specified value

 
• Simulated Telephone Sensitivity  None (for infor purposes only)

• Designed to test non-linear Hearing Aids with Broadband signals
• Gives Family of 4 Response Curves
• Inputs range from 40 to 90 dB SPL

Following graph taken from information in the Frye Electronics manual.  Additional information available from:  
        http://www.frye.com