Measuring System for Hearing-Protection Devices
Hearing Protector Test System Nor838 is used for the determination of the sound attenuation of hearing protectors using the subjective method (ISO 4869 part 1) and is performed by two measurements of hearing thresholds. The sound attenuation of the hearing protector is the difference, in decibels, between the thresholds of hearing with and without the hearing protector in place for a test subject. The threshold of hearing with open ears and with hearing protector in place must be measured once for each test subject in accordance with ISO 8253 part 2. The software Nor4869 in combination with the instrument Nor838 and a room with reproduction devices provides two methods to determine hearing thresholds. The Békésy method and the method of “just noticeable differences”. In addition several methods to process the data are selectable by the operator. The measurements are conducted in a diffuse sound field which is generated by four loudspeakers placed in the corners of a (virtual) tetrahedron. The loudspeakers are fed by four uncorrelated noise sources. The test signal is one-third octave band-filtered random noise with centre frequencies 63 Hz (optional), 125 Hz, 250 Hz, 500 Hz, 1000 Hz, 2000 Hz, 4000 Hz and 8000 Hz.
- Complete system with 4 uncorrelated signal generators, amplifiers and speakers.
- Very flexible test sequence set up
- Built-in database for
- – test subjects
- measurement organization
- report generation from a large number of individual measurements
- handles several parallel studies
- Calibration tool and sound field control using a sound level meter
- Determination of the sound attenuation of hearing protectors using subjective methods
- Finding the hearing thresholds using the Békésy or JND methods
- Pure tone Audiometer measurements Standards applicable
- ISO 4869-1 • ANSI ASA S12.6
- ISO 8253-1
- ISO 8253-2