AOSafety E-A-RTONE 3A manual Background Noise Reduction, Obtained Interaural Attenuation

	125	250	500	1000	2000	4000	Hz
							8000
	-10
dB	0
	10
	20
	30
	40
	50
	60
	70
	80
	90
	100
	110
			Obtained Interaural Attenuation
			Full E-A-RLINK insertion in both ears
			Shallow insertion in dead ear only
			Shallow insertion in both ears

2. Background Noise Reduction

A major benefit of the E-A-RTONE®Insert Earphone in combination with the E-A-RLINK®disposable foam eartips is the reduction of background noise that might interact with the presented pure tones and influence the threshold determinations. When hearing tests are performed outside a standard audiometric test booth and the E-A-RLINK®eartips are fitted to the subject according to the instructions, the expected noise attenuation will typically exceed 30 dB in the frequency region 125-8000 Hz. This additional attenuation will improve test precision in non-ideal environments and, in most cases, allow testing down to 0 dB HL in a background noise level not exceeding 45 dB(A).

The latest ANSI Standard (ANSI S3.1-1999) “Maximum Permissible Ambient Noise Levels (MPANLs) For Audiometric Test Rooms” Table 1 and Table 2 includes octave band and one-third octave band permissible noise levels for both supra-aural and Insert Earphones. The ANSI octave band MPANLs are presented below for standard earphones and also for E-A-RTONES®with fully inserted E-A-RLINKS®.

ANSI S3.1-1999 - Ears covered: octave band MPANLs using a supra-aural or insert earphone for three test frequency ranges re: 20? Pa to nearest 0.5 dB.

Octave

Band

Intervals

125

250

500

1000

2000

4000

8000

Supra-aural Earphone

125	-	250	-	500	-
8,000	Hz	8,000	Hz	8,000	Hz
35.0		39.0		49.0
25.0		25.0		35.0
21.0		21.0		21.0
26.0		26.0		26.0
34.0		34.0		34.0
37.0		37.0		37.0
37.0		37.0		37.0

E-A-RTONE Full Insertion

125	-	250	-	500	-
8,000	Hz	8,000	Hz	8,000	Hz
59.0		67.0		78.0
53.0		53.0		64.0
50.0		50.0		50.0
47.0		47.0		47.0
49.0		49.0		49.0
50.0		50.0		50.0
56.0		56.0		56.0

The ears covered MPANLs shown in the above table were derived using mean earphone attenuation values. To decrease the chance that individual listeners for whom less than average attenuation is obtained will experience threshold shift, the MPANLs can be lowered by reducing the amount of earphone attenuation. An appropriate reduction would be equal to the mean attenuation minus one standard deviation. The net effect would be that the MPANLs would be lower (more stringent) for ears covered testing. This reduction would cover about 84% of all subjects. The standard deviations for Insert Earphones for 125 to 8000 Hz are between three

(3) and six (6) decibels. Please refer to ANSI S3.1 – 1999, Table A.2 for specific standard deviation values by frequency.

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