4
Frequency [Hz]
125
250
500
1000 2000
3150
4000
6300
8000
NRR
CSA
Class
MT7H7A4610-NA
Head band
Mean Attenuation [dB]
17.8
23.0
32.1
36.2
35.1
39.0
38.7
38.3
36.5
25
A
Standard Deviation [dB]
4.4
3.2
2.8
3.0
2.4
3.8
3.0
3.5
3.9
MT7H7B4610-NA
Neck band
Mean Attenuation [dB]
18.9
25.9
35.2
37.0
34.9
40.6
39.9
39.7
39.7
26
A
Standard Deviation [dB]
5.2
3.2
3.3
2.9
2.5
3.6
3.0
2.3
2.5
MT7H7P3E4610-NA
Helmet attachment
Mean Attenuation [dB]
19.4
24.3
33.6
35.5
34.1
38.5
38.0
35.8
35.7
25
A
Standard Deviation [dB]
3.4
3.3
3.8
1.7
2.6
3.6
3.1
5.4
5.4
Testing performed by E-A-RCAL lab first accredited 12/3/91. All data per ANSI S3.19-1974.
(K) Attenuation
The NRR calculated from these laboratory-based attenuation data is 25. Improper fit of this device will reduce its effectiveness in
attenuating noise. Consult the fitting instructions for proper fit.
The level of noise entering a person’s ear. when a hearing protector is worn as directed, is closely approximated by the difference
between the A-weighted environmental noise level and the NRR.
Example:
1. The environmental noise level as measured at the ear is 92 dBA.
2. The NRR is 25 decibels (dB).
3. The level of noise entering the ear is approximately equal to 67 dBA.
Caution: For noise environments dominated by frequencies below 500 Hz, the C-weighted environmental noise level should
be used.
Although hearing protectors can be recommended for protection against the harmful effects of impulsive noise, the noise
reduction rating (NRR) is based on the attenuation of continuous noise and may not be an accurate indicator of the protection
attainable against impulsive noise such as gunfire.
Improper fit of this device will reduce its effectiveness in attenuating noise. Consult the fitting instructions for proper fit.
1
2
3
(J)
(I) DCS (Digital Coded Squelch)
39.
023
53.
114
67.
174
81.
315
95.
445
109.
631
40.
025
54.
115
68.
205
82.
331
96.
464
110.
632
41.
026
55.
116
69.
223
83.
343
97.
465
111.
654
42.
031
56.
125
70.
226
84.
346
98.
466
112.
662
43.
032
57.
131
71.
243
85.
351
99.
503
113.
664
44.
043
58.
132
72.
244
86.
364
100.
506
114.
703
45.
047
59.
134
73.
245
87.
365
101.
516
115.
712
46.
051
60.
143
74.
251
88.
371
102.
532
116.
723
47.
054
61.
152
75.
261
89.
411
103.
546
117.
731
48.
065
62.
155
76.
263
90.
412
104.
565
118.
732
49.
071
63.
156
77.
265
91.
413
105.
606
119.
734
50.
072
64.
162
78.
271
92.
423
106.
612
120.
743
51.
073
65.
165
79.
306
93.
431
107.
624
121.
754
52.
074
66.
172
80.
311
94.
432
108.
627
