HP RM500SL manual Broad-band signals

microphone.

2.2Broad-band signals

2.2.1Pink Noise signal

The pink noise signal is available for Multicurve 2 cm3 coupler gain and output frequency response measurements and for Insertion gain and Speechmap real-ear measurements. It is a pseudo-random signal composed of 1024 simultaneous tones summed to provide a crest factor of 12 dB. The spectrum of the pink noise signal is controlled by the reference microphone in conjunction with a digital feedback loop with a frequency resolution of 1/12 octave and a response time of about 1/3 of a second. Pink noise was selected as a test signal because it has equal energy per octave, producing a flat spectrum when analyzed in 1/12 or 1/3 octave bands. Figure 1 shows the 1/3 octave spectrum of the pink noise signal and the noise signal specified in ANSI S3.42-1997. Note that the ANSI S3.42-1997 spectrum represents speech peaks not the long-term average.

1/3 OCTAVE SPECTRA for the PINK NOISE SIGNAL

and ANSI S3.42 NOISE re overall SPL

-8.00

Band Level re overal SPL - Pink Noise

	-9.00											Band Level re overall SPL - ANSI S3.42
	-10.00
SPL)	-11.00
re overall	-12.00
	-13.00
SPL (dB
	-14.00
BAND	-15.00
	-16.00
	-17.00
	-18.00
	200	250	315	400	500	630	800	1000	1250	1600	2000	2500	3150	4000	5000	6300	8000

BAND CENTER FREQUENCY (Hz)

Figure 1: 1/3 octave spectra for the pink noise signal and the noise signal specified in ANSI S3.42- 1997.

2.2.2Dual-direction pink noise signal (Verifit only)

This unique test signal is available in the dual-source Verifit test chamber and for real-ear measurements by adding an additional sound-field speaker. It is similar to the pink noise signal described previously except that the component tones are presented simultaneously from two speakers, half from each. The level of each tone is independently controlled at the reference microphone. Two frequency response curves are generated simultaneously -one for each speaker. This provides a real-time measure of the functioning of the directional features of hearing aids that is independent of compression or noise reduction algorithms. Measurement methods which sequentially measure response from different directions work only with these features disabled.

2.2.3Real-speech signals

Real-speech signals are provided in Speechmap for both REM and S-REM measurement modes. Four different

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