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| Content Provider | The American Society of Mechanical Engineers (ASME) Digital Collection |
|---|---|
| Author | Kinnerup, Rasmus Trock Knott, Arnold Thomsen, Ole Cornelius Marbjerg, Kresten Rasmussen, Per |
| Abstract | Measuring infrasonic sound sets high requirements on the instruments used. Typically the measurement chain consists of a microphone and a preamplifier. As the input resistance of the preamplifier forms a high pass filter with the capacitance of the microphone in the picofarad range, measuring ultra low frequencies becomes a challenge. The electric preamplifier presented in this paper together with a prepolarized condenser microphone form a measurement system. The developed preamplifier connects the microphone signal directly to the input of an operational amplifier with ultra high input impedance. The bias current for the preamplifier further complicates the signal amplification. A configuration of two diode-connected FETs provide the input bias current. The resulting input impedance of nearly 1 TΩ yields a total lower limiting −3 dB cutoff frequency of 8 mHz and a dynamic range of 95 dB. Being able to measure down to ultra low frequencies in the infrasonic frequency range will aid actors in the debate on wind turbine noise. Sonic booms from supersonic flights include frequencies down to 10 mHz and the preamplifier proposed in this paper will aid scientists trying to modify the N-shaped shock wave at high level which prohibits flights in land zones. |
| Sponsorship | Noise Control and Acoustics Division |
| Starting Page | 605 |
| Ending Page | 616 |
| Page Count | 12 |
| File Format | |
| ISBN | 9780791845325 |
| DOI | 10.1115/NCAD2012-1468 |
| Volume Number | ASME 2012 Noise Control and Acoustics Division Conference |
| Conference Proceedings | ASME 2012 Noise Control and Acoustics Division Conference at InterNoise 2012 |
| Language | English |
| Publisher Date | 2012-08-19 |
| Publisher Place | New York City, New York, USA |
| Access Restriction | Subscribed |
| Subject Keyword | Noise (sound) Chain Filters Condensers (steam plant) Measurement systems Flight Capacitance Instrumentation Signals Microphones |
| Content Type | Text |
| Resource Type | Article |
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