Mid-High frequency volume acceleration sound source

Volume acceleration sound sources are sophisticated acoustic excitation devices that produce high levels of sound or noise. The E-MHFVVS covers the 200 to 10000 Hz frequency band and provides an accurate real time signal of the acoustic output.

The mid to high frequency source is a tube type of source, the sound is generated in a high pressure driver and transferred to the nozzle by a flexible tube. The nozzle, placed at the location or the ear, produces the noise The instrumented nozzle produces noise through a small opening. The nozzle is so small that the omni-directionality of this source becomes comparable to the directionality of a ½ inch microphone. The nozzle also allows positioning in narrow spaces around the engine, exhaust, under a dashboard etc.

The mid to high frequency volume acceleration sound source has a whole list of properties to recommend it. Positioning flexibility, high impedance, compact size, omni-directionality, time stable calibration, high noise levels, and real-time volume acceleration signal. These qualities make this device extremely accurate and efficient to use for the analysis of transportation vehicles like cars, vans, trucks, busses, trains and aircraft and their systems like engines, transmissions, dashboard modules.

The mid to high frequency source is typically used for TPA of structure borne or airborne contribution, experimental SEA testing, vibro-acoustic modal analysis of smaller spaces, airborne isolation and radiation investigations, etc.

General Functionality:

Point source for accurate acoustic excitation, real-time volume acceleration output signal
Output volume acceleration sensor integrated and environment and time stable
Easy to position on a seat, in the engine compartment or anywhere
High volume displacement level at compact size
High acoustic impedance
Useful frequency range @ 200 to 10000 Hz
Constant sensitivity value of the output signal
Omni-directional point source
Negligible diffraction

Technical specifications

Size, nozzle dimensions: Round 27mm, length 45mm
Size, tube length: 4.25 m
Weight excluding cable: 18 Kg
Effective frequency range: 200 to 10000 Hz
Constant real-time output signal freq. range: 200 to 10000 Hz, +-4 dB
Output volume acceleration sensitivity: 600 m 3/s2V nominal
Output signal conditioning requirement : ICP
Free field omnidirectionality freq. Range: 200 to 10000 Hz, +-4 dB
Source input impedance: 10 Ohm nominal
Required signal output impedance: 10 KOhm
Maximum input current: limited by a F1A fuse
Minimal power amplifier requirement: 100 Watt and 24Volt (RMS)
Maximum sound pressure level in semi free field***: 100 dB SPL at 1m

Note: Performance and dimensions of the device, as stated above, are an indication only. The actual values of the delivered product can deviate from the given specification. However, in most of such cases the specifications will exceed the given ones above, because of improvements in the used materials and design.
*** When using continuous broadband random noise 200 to 10000 Hz, of low crest factor.

Applications

ASQ, contribution analysis
Mostly for power-train/drive-line, and the intake and exhaust system. It is sometimes used on tires, ventilation system, interior trim, steering system, etc. Typical instrumentation includes the Scadas III : 16 channels or more, two E-MHFVVS on two seats and in semi-free field, large number of accelerometers and microphones. The software used for this includes F-mon, TPA and RMA.
Advantages include; more then sufficient excitation, fast instrumentation, and efficient parallel measurement of large number of acoustic FRF.

Isolation, Absorption, and SEA Tests
For isolation, absorption, and SEA tests on car- and truck- bodies, sometimes used on aircraft fuselage, aircraft APU machinery encapsulation, etc. A typical instrumentation includes Scadas III : 16 channels or more, two E-MHFVVS on two seats (and other locations), and a large number of accelerometers and microphones. The software used is typically F-mon, TPA and RMA.
The advantage of this method, using the mid to high frequency source is that you easily attain a more than sufficient excitation level, the instrumentation is fast, and you can do very efficient reciprocal parallel measurements of a large number of acoustic FRFs.

Vibro-acoustic modal analysis
Mostly used in smaller cavities such as engine bays, induction systems, ventilation systems, etc. The instrumentation for modal analysis with mid to high frequency sources includes Scadas III : 16 channels or more, two E-MHFVVS, several microphones in the cavity and several accelerometers on the panels and other structures. The software used with the sources includes F-mon, acoustic modal, and modal design. The advantage to using these sources is that they allow scaled modal models, a high excitation level and do not disturb the sound field by their size.

Vibro-acoustic Transfer Path Analysis
Mostly used on engines and other machinery to investigate internal contributions and the vibro-acoustic sensitivity of a structure. Sometimes used on cars and trucks to study mid frequency structure borne sound from the engine and transmission as well as for smaller equipment like ventilation units, steering, and electro-motors.
Typical instrumentation for this application includes Scadas III : 16 channels or more, two mid to high frequency sources, a large number of accelerometers and some microphones. The software used is F-mon, TPA, and RMA.
The sources provide users with more then sufficient excitation, fast instrumentation and efficient parallel measurement of large number of vibro-acoustic FRFs.

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