The structure is made portable to achieve a high degree of freedom of location. This, combined with the easy, toolless assembly in minutes, enables you to save expensive anechoic chamber time and to offer on-site sound power diagnostics.
The G.R.A.S. hemisphere is compliant with the ISO 3746:2010 (ANSI S12.56) standards and accommodate for 4 positions. These are clearly marked to ease the mounting and maintain measurement repeatability. Two hemisphere structures are available; a 1 m measurement radius and a 2 m measurement radius.
The G.R.A.S. 67HA-04 1 m CCP Hemisphere kit, 4 channels includes
- 1x Hemisphere structure
- 4x G.R.A.S. 46AE 1/2” CCP Standard Microphone Sets, cables, holders
- 2x Flight cases
Typical applications and use
Depending on the size and the emitted acoustic level of the DUT, the hemispheres will allow sound power measurements on everything from small sized personal electrics to office machines and IT products, household appliances, power tools and smaller engines. The only restriction is, that the characteristic dimension of the DUT may be no more than half the measurement radius.
The hemispheres are available as preconfigured kits with 4, 10 or 20 microphone sets in 3 variations; CCP, LEMO and low-noise LEMO. In the table to the right you will be able to find the hemisphere kit that suits your type of input module along with dynamic specifications for your application. The pre-configured hemispheres are delivered with microphone set holders that will fit all 3 microphone types. Respective cables and cable clips are included and everything are delivered in high-quality flight cases.
The recommended microphone sets can be connected directly to all professional measurement systems and are as indicated available for both CCP and 7-pin LEMO inputs. If your system platform supports intelligent transducers according to IEEE 1451.4 (TEDS), the system can be set up to identify the microphone properties and position in the array.
All included microphone sets are delivered with individual calibration charts including sensitivity values and frequency responses. These sensitivity values can be used directly in your system setup.
For frequent measurement chain verification a reference sound source will be required. G.R.A.S. supplies 114 dB types for the standard microphone sets and a special 94 dB adapter for the low-noise sets. Depending on the use and your internal quality control requirements we recommend that the sets are re-calibrated at least every second year.
|Frequency range (±2 dB)||Hz||3.15 to 20k|
|Dynamic range lower limit with G.R.A.S. preamplifier||dB(A)||17|
|Set sensitivity @ 250 Hz (±2 dB)||mV/Pa||50|
G.R.A.S. 67HA 1m CCP Hemisphere kit
Reference sound sources
|G.R.A.S. 42AB||Sound Level Calibrator (114 dB)|
|G.R.A.S. 42AP||Intelligent Pistonphone (114 dB)|
|G.R.A.S. RA0090||Pistonphone Coupler for G.R.A.S. 42AP|
|G.R.A.S. AA0037||For CCP Microphone sets: 10 m BNC-BNC cable|
|G.R.A.S. AA0009||For LEMO Microphone sets: 10 m LEMO-LEMO cable|