Aearo Company E-A-RTONE 3A - Manual (Page 4)

3
-10
0
10
20
30
40
50
60
70
80
90
100
110
125 250 500 1000 2000 4000 8000
Hz
dB
Full E-A-RLINK insertion in both ears
Shallow insertion in dead ear only
Shallow insertion in both ears
Obtained Interaural Attenuation
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.
Supra-aural Earphone E-A-RTONE Full Insertion
Octave
Band
Intervals
125 -
8,000 Hz
250 -
8,000 Hz
500 -
8,000 Hz
125 -
8,000 Hz
250 -
8,000 Hz
500 -
8,000 Hz
125 35.0 39.0 49.0 59.0 67.0 78.0
250 25.0 25.0 35.0 53.0 53.0 64.0
500 21.0 21.0 21.0 50.0 50.0 50.0
1000 26.0 26.0 26.0 47.0 47.0 47.0
2000 34.0 34.0 34.0 49.0 49.0 49.0
4000 37.0 37.0 37.0 50.0 50.0 50.0
8000 37.0 37.0 37.0 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.