Does the HEARLab® have to be calibrated before use?
The insert earphones and bone conductor are calibrated at the factory prior to shipment. They should be recalibrated on a regular basis (e.g. yearly). The calibration procedure is described in the HEARLab® Maintenance Manual which can be referenced for more information.
Calibrating the free field loudspeaker used during ACA testing should be done more often, and definitely when the layout of the testing room has been changed, or when the system has been moved somewhere else.
How do I calibrate the free field loudspeaker for ACA testing?
The Free Field Calibration Wizard will guide you step-by-step through the calibration process. See chapter 4 of the HEARLab® manual for more information.
I cannot find the calibration screen to calibrate the ACA loudspeaker?
Press (same time) – Ctrl+Alt+Shift+K
Should the speaker be raised to 1.2 metres (as per the HEARLab® manual) or can it be placed at the level of the subjects head or lower?
See Chapter 4 of the HEARLab® manual.
The diagram has been designed according to some norms for free field testing, which require a minimum of 1.2 metres from any walls, floors etc. Of course sometimes this is not possible due to practical reasons (small room) or not desirable if the child’s head is lower than this level.
If the loudspeaker is too close to the wall or any other object the calibration has a higher likelihood of failure. But if you’re able to complete the entire calibration process successfully, all is well.
Aim for the speaker to be directly in front of the subject’s head and the calibration with the microphone at that position. As long as the person’s head is at a similar position to where the microphone was during the calibration, then it shouldn’t be too much of a problem. Most importantly, it should be in front the child so as not to give an advantage to one ear in particular.
Is it possible to have the distance between the loudspeaker and the subject’s head position more than 1.2 metres (4 feet)?
This is possible if an external power amplifier driving a higher power loudspeaker is used. Two sockets located at the back of the Stimulus Controller labelled “To Amplifier” and “From Amplifier” is provided to facilitate such a setup. See the Maintenance Manual for more information on using a two-room setup, including a diagram of the amplifier sockets.