NDLI: Microphone Probe for In-Duct Measurement of Gas Turbine Exhaust Noise

Content Provider	The American Society of Mechanical Engineers (ASME) Digital Collection
Author	Sacks, M. P. Kawall, J. G. Behboudi, R. Buttell, J.
Copyright Year	2000
Abstract	A new probe has been developed for Bruel & Kjaer 6.35 mm (1/4″) microphones in order to allow in-duct measurements in high temperature gas turbine exhaust ducts without exposing the microphone to excessive temperatures. The motivation for this design was the need for a probe system that is easily transported and installed on site. The new probe is made from readily available 6.35 mm (1/4″) o.d. tubing and compression fittings. It consists of a stem to sample the in-duct acoustic field, a shut off valve, a “T” connector to provide a microphone port remote from the hot gas and an anechoic termination. The termination provides a true anechoic response down to 20 Hz. The probe provides a smooth, resonant free response between 20 Hz and 20 kHz allowing for accurate calibration and measurement. This paper describes the probe design and installation details, probe frequency response calibration, probe flanking limit and performance of the anechoic termination. The paper also compares the probe response to theoretical predictions. Relative to other potential in-duct measurement probe systems the new design is seen to be lightweight, compact and inexpensive.
Sponsorship	International Gas Turbine Institute
File Format	PDF
ISBN	9780791878552
DOI	10.1115/2000-GT-0349
Volume Number	Volume 2: Coal, Biomass and Alternative Fuels; Combustion and Fuels; Oil and Gas Applications; Cycle Innovations
Conference Proceedings	ASME Turbo Expo 2000: Power for Land, Sea, and Air
Language	English
Publisher Date	2000-05-08
Publisher Place	Munich, Germany
Access Restriction	Subscribed
Subject Keyword	Compression Temperature Ducts Valves Acoustics Calibration High temperature Exhaust systems Microphones Noise (sound) Design Fittings Gas turbines Tubing Frequency response Resonance Probes
Content Type	Text
Resource Type	Article

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