HP RM500SL manual FastFacts 20.4 HIT curves inconsistent

20.3 HIT high distortion or noise

High distortion and/or noise numbers in an ANSI test

vThere may be a leak between the hearing instrument under test and the coupler it is connected to. For BTE type instruments, check the integrity of the #13 tubing at the end of the coupler where it joins with the ear hook. Look for cracks. ITE type instruments need to have a good seal between the hearing instrument and the coupler. In addition, all vents need to be closed from the faceplate side of the hearing instrument.

vAmbient room noise may be leaking into the test chamber. Air conditioners, computer fans and similar noisemakers can yield artificially high noise figures. Check the sealing of the test chamber. Try turning off suspected noise sources to identify the cause.

vVibration may be coupled into the test chamber from other equipment on the same table or wooden floor. Computers, fans and air conditioners may be the source of the vibration. Try turning off suspected sources to identify the cause. Relocate the source or the RM500SL or mount it on a foam pad.

FastFacts 20.3: HIT high distortion or noise 20.4 HIT curves inconsistent

The HIT curves keep changing from test to test.

vThe battery may be close to end of life or starved for air (zinc-air cells) because of a tight seal on the battery compartment. Try a fresh battery or using the optional RM500SL battery pill.

vThe HIT reference microphone (the white one in the test chamber) is incorrectly positioned. In order to control sound pressure levels precisely at the microphone inlet of the hearing instrument, the HIT reference microphone must be positioned as close as possible to the hearing instrument’s microphone without actually touching it.

vThe noise or feedback reduction features are attempting to reject the test signal. These need to be disabled prior to tests with tones or noise.

vThe instrument is on the verge of feedback due to a poor seal to the coupler, unplugged vent or a crack in the tubing on the BTE coupler.

FastFacts 20.4: HIT curves inconsistent

0611 RM500SL User’s Guide Version 2.8 Page 89