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IntroductionG.R.A.S. Sound & Vibration offers the most comprehensive selection of microphones in the industry. Please browse the categories below and click on the links to see the specific models we offer in that category. This Selection Guide for Microphones may be helpful in understanding the fundamental characteristics and differences of microphones.
All microphones provided by G.R.A.S. Sound & Vibration are constructed with a stainless steel protection grid and housing as well as special stainless alloy diaphragm for unmatched durability and longevity. All our high precision - type 1 - measurement microphones are delivered with a five year warranty against defective materials and workmanship. |
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Free Field Microphones
A free-field microphone is designed to measure the sound pressure in a sound field and compensate for the influence of its presence in the sound field.
A free-field microphone measures the sound pressure as it existed before the microphone was introduced into the sound field; in effect, maintaining free-field conditions.
A free-field microphone should be pointed towards the sound source, i.e. at an angle of 0º incidence to the source.
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Pressure Microphones
A pressure microphone is used, typically, in coupler measurements and, when flush-mounted on a wall for example, for sound-pressure measurements on the surface of the wall. In such applications, the effect of the microphone's presence in the sound field is intended.
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Random Incidence Microphones
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Array Microphones
They are also of particular value when measurement opportunities are few and far between either because of costs or repeatability.
The Array Microphone Types 40PH and 40PL are low-cost microphones for general-purpose measurements in arrays and matrices. They have a wide useful frequency range reaching up to and a large dynamic range topping at around 134 dB. They have an integrated CCP* preamplifier and built-in TEDS** enabling them to be programmed as a complete unit.
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Low Noise Level Microphone Systems
A quiet location can easily be subjected to intrusive noise when many otherwise "inaudible" devices are in use.
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Surface Microphones
It must be possible to flush mount it on planar and curved surfaces and be little affected by the curvature of the surface at the mounting point.
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Outdoor Microphones
Perching birds and their excreta can seriously distort measurements or even overload the measurement equipment. Smaller birds have actually been known to nest on top of the earlier three-pronged anti-bird spikes. Hence, the introduction of the fourth, centre prong.
Two versions are available: one with the measurement direction pointing upwards (0° incidence, for airport noise monitoring) and one with the measurement direction in the horizontal plane (90° incidence, for community noise- or traffic noise measurements).
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Probe Microphones
Its right-angle design makes the probe microphone particularly well suited for measurements on exhaust systems and other machinery in general, as well as for scanning surfaces such as loudspeaker cones and loudspeaker cabinets.
Its very small size, low weight and all stainless-steel construction, make the probe robust, easy to handle and simple to mount.
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Environmental Microphones
As with Outdoor Microphones, these G.R.A.S. Environmental Microphones are equipped with four-pronged anti-bird spikes on top of the windscreen. This prevents birds from perching on top of the windscreen when the microphone unit is placed outdoors for long-term unattended noise surveillance.
Birds perching on top of the windscreen can seriously disturb measurements or even overload the measurement equipment. Furthermore, bird excreta can distort the acoustic properties of the windscreen so that it no longer performs according to original specifications.
Some smaller birds have actually been known to nest on top of the earlier three-pronged anti-bird spikes. Hence, the introduction of a fourth, centre prong.
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Window Microphones
It can also be used to provide a useful assessment of current or improved sound proofing in buildings continuously exposed to external noise, e.g. from road traffic.
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A pressure microphone is designed to measure the sound pressure that actually exists in front of its diaphragm. This means that the microphone also measures any changes in the sound field brought about by the presence of the microphone.
A random incidence microphone is designed essentially to measure sound pressure levels in a diffuse sound field as they existed before the microphone was introduced into the diffuse sound field. At higher frequencies, the presence of the microphone in the sound field becomes more significant and will influence the measured sound pressure levels.
Array microphones are used in situations where concurrent measurements are required at several points. For example in the analyses of:
G.R.A.S. Low-noise measuring systems can measure noise levels below the threshold of human hearing, e.g. from disk drives, computer equipment in general and in quiet rooms.
A surface microphone is for use in places where sound measurements are performed in the presence of air flow, e.g. on the external surfaces of vehicles either in motion or in wind tunnels.
Outdoor Microphones are for permanent outdoor use and are encased in stainless steel units that can withstand all weathers year after year e.g. in airport noise monitoring systems.
A window microphone is a useful tool for measuring community noise striking the facades of, say, hospitals, offices and dwellings.
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