Performing a measurement

Preparation:

Before the actual measurement begins, guide your patient through the orientation/training procedures. Also provide your patient with the AHA Scaling test form during the orientation/training procedures as well as during the actual test procedures.

See the image below as a reference for testing with open headphones (Figure 218). The open headphones will ensure proper calibration with the presentation signal.

Figure 218: Loudness scaling procedure with open headphones

There are similar, but different test procedures for scaling with or without hearing aids. See the section "Scaling: Operation" for more details.

Scaling without a hearing aid provides insertion gain data; this data can be used to pre-program the hearing aids. For scaling procedures with open fit hearing aids, using real ear measurements is recommended. If a patient presents with a progressive hearing loss, it is possible that the output limits within the scaling procedures (100 dB) are not sufficient. In this case, you should perform the measurement in the with the hearing aids mode.

For re-adjustments or fine tuning procedures the with the hearing aids mode is recommended for faster procedures.

Measurement in the without a hearing aid mode, shows the differences in gain from the generated targets. Measurement in the with the hearing aids mode, shows the loudness differences (gain) between the hearing aid gain and the generated targets.

Performing the scaling procedures in the with the hearing aids mode followed by the actual hearing aid measurements will generate target values for the test box. This setup was designed so that patients would be comfortable during hearing aid adjustments. Special features of the hearing aids, such as the directional microphones and noise reduction features, need to be disabled during the scaling procedures. The scaling procedures are performed using narrow band noise signals, which could activate the special hearing aid features and distort the actual measurements. The AGC parameters of the hearing aids, such as the audiological parameters, need to be enabled during testing. As discussed in previous sections, while in the with the hearing aids mode, it is necessary to perform a measurement directly in the test box following the scaling procedures in order to determine the gain of the hearing aids.

Measurement without Hearing Instrument:

	Following a scaling procedure, the collected data can be applied to other sections for further testing. If target values mode is selected within the ACAM System, it is possible to view the target curves immediately after the measurement is completed.
	To view the test box or real ear measurement curves, select the following boxes within the Target Gains window: Show AHA target constructions Specific curves can be hidden or shown: select the specific input levels and frequencies that you would like to have displayed.
	Following the above selections, target values for real ear measurements will be displayed. Adjustments can be made to match the insertion gain targets for the different input levels. The example to the left shows input levels of 50, 65, and 80 dB.
	If you select to convert the real ear gain curves into coupler curves, the target curves for the test box measurements can be simulated.

Measurement with Hearing Instrument:

Following the scaling procedures, the hearing aids need to be measured in the test box. This step generates target curves to determine the gain of the hearing aids being used. Deviations from the reference and normal curves will be added to the measured values.

The above steps results in the hearing aid measurement target values: the AHA target values for the scaling procedures measured with the hearing aids.

To view the test box or real ear measurement curves, select the following boxes within the Target Gains window:

Show AHA target constructions
Specific curves can be hidden or shown: select the specific input levels and frequencies that you would like to have displayed.

Parameters in the test box can be adjusted to match the generated target values. The example to the left shows the AHA target values with hearing aids for input levels of 50, 65, and 80 dB. It also shows the hearing aid response curves prior to adjustments at 50, 65, and 80 dB.

The differences in gain between the hearing aid and the target values are displayed. In the example to the left, the gain is too low at low input levels. With increasing input, the hearing aid gain is closer to matching targets. In this example, more gain would be required in order for the hearing aid to match targets. The AGC would also need to be increased because more gain is needed at higher input levels.

For more information regarding scaling measurements, please refer to the section: "Scaling: Operation."