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ANSI characteristics
Hearing aids 2 exam 1-3
| Question | Answer |
|---|---|
| Tympanoplasty: | replaced TM |
| ANSI standards governs: | the testbox |
| ANSI S3.22-1996 | intended to meet the need for specifications of air-conducted hearing aid performance parameters and their tolerances;for comparing performance characteristics of different hearing aids or for comparing characteristics of a hearing aid with specs |
| Reference SPL | An RMS value expressed in decibels relative to 20 uPa |
| Input SPL: (for non directional hearing aids: | the SPL at the microphone opening of the hearing aid |
| Input SPL: (for directional hearing aids) | the SPL in a progressive sound field adjacent to the microphone opens of the hearing aid |
| Acoustic gain: | difference between the output SPL in an earpohne coupler and the input SPL |
| Gain control: | user-operated for the adjustment of gain (VC)- Amplifier is always putting out the same gain. The volume control adds friction to make it sound softer |
| Output SPL for a 90 dB input signal: | SPL developed in a 2cc coupler when the input SPL is 90 dB, with the gain control of the hearing aid full-on, termed OSPL 90 |
| OSPL | output SPL when 90 dB goes in the HA 90 dB puts HA into saturation( no matter what you do, it cannot go any louder) |
| High Frequency average (HFA) output SPL for a 90 dB input: | the average of 1000, 1600, 2500 Hz, termed HF OSPL 90 |
| Special purpose average (SPA) | average of the frequencies specified by the manufacturer |
| Full-on-gain: | acoustic gain when the gain control of the hearing aid is at the full-on-position (max gain, max output, boradest frequency response, minimal compression) |
| HFA full-on-gain: | average of 1000, 1600, 2500 Hz of the full-on-gain curve |
| RTS/Reference Test Gain (RTG): | acoustic gain of a hearing aid when its gain control is set to amplify a 60 dB SPL input signal to a level in the coupler that is 17 dB below the HFA OSPL 90 value for the hearing aid. Turn down the gain until reaching target which is HFA OSPL90-17dB |
| Automatic Gain control (AGC)hearing aid: | hearing aid incorporating means, other that peak clipping, by which the gain is automatically controlled as a function of the magnitude of the signal being amplified |
| When would you use 50 vs 60 dB SPL? | Use 50 dB if you have a HA with compression on it or if the full on gain comes anywhere near 60dB + 60 dB |
| Input-Output function (i/o): | single frequency plot of the coupler SPL on the ordinate as a funtion on input SPL on the abscissa with equal decibel scale divisions on each axis |
| SPLITS: | coupler SPL for an inductive telephone simulator: SPL developed in a 2cc coupler by a hearing aid with the gain control in the RTG position when the input is a magnetic field generated by a telephone magnetic field simulator (used for t-coil)- |
| HA 1 couplers are used for: | all variations of custom products |
| HA 2 couplers are used for | BTEs |
| Curves generated in test box: | OSPL 90 curve HFA-OSPL90 curve Full-on-gain(FOG) curve HFA FOG curve |
| OSPL 90 CURVE: | curve of the coupler SPL versus frequency over the range of 200-5000 Hz, using a constand intput SPL of 90 dB. The maximum SPL shall not exceed that specified by the manufacturer + 3dB |
| HFA-OSPL 90 | average of 1000,1600 and 2500 dB This tolerance shall be within +/- 4dB of specified values (this is what you are setting as maximum output!!) |
| Full-on gain (FOG)curve: | curve of the coupler SPL versus frequency over the range of 200-5000 hz, using a constant input SPL of 50 or 60 dB. |
| HFA FOG curve: | average of 1000, 1600, and 2500 dB. This tolerance shall be within +/- 5 dB of the manufacturers specified value |
| Measurements run in RTG position: | Frequency response curve frequency range harmonic distortion equivalent input noise (EIN) level battery current drain SPLITS curve |
| Frequency response curve: | with an input of 60 dB (50 dB for AGC hearing aids) generate a curve. |
| Frequency range: | From the frequency response curve, average 1000,1600, 2500 subtract 20 dB draw a horizontal line parallel to the frequency axis f1: lowest freq at which resp curve intersects horizontal line f2: highest freq at which resp curve intersects horizontal l |
| harmonic distortion: | the harmonic distorion is measured at the following frequencies at the indicated intensity: 500Hz @ 70 dB 800 Hz @ 70 dB 1600 Hz @ 65 dB Tolerance: no greater than 3% above mfrs specs (if more than 8%... distortion in a HA-> HA will not meet ANSI str |
| Equivalent Input noise (EIN) | Ln: determins the avg of 1,1.6 and 2.5 Khz (LAV) with an input SPL of 60dB. Remove the input signal & record the SPL in the coupler caused by the inherent noise. Ln=L2-(LAV-60)dB Tolerance: The EIN level shall not exceed the max value spec by mafr +3dB |
| Battery current: | using a 1000 hz tone signal at an input of 60 dB, record the battery drain in mA Shall not exceed maximum value as specified by manufacturer plus 20% |
| SPLITS curve: | with the hearing aid set to the t position, position the hearing aid for maximum output, record coupler SPL as a function of frequency in the range 200-2000 Hz |
| HFA SPLITS curve: | tolerance shall be within +/- 6dB |
| compression: | gain reduction in input signal |
| attack time: | how fast it takes for HA to go into its compression mode (when in compression mode) |
| release time: | how quickly it takes to go back to a normal signal |
Created by:
azcanfield