AUTHORS: Adhwa Amir Tan, Nurliza Salim, Noor Hidayah Tauhid Ahmad, Syahrim Azhan Ibrahim, Maszlan Ismail

Download as PDF

ABSTRACT: Reverberation acoustic chamber has been designed to stimulate as many mode as possible over the frequency spectrum in line to simulate the launching stage and define strength and stress on the test object. Launching stage is producing highly intensity of acoustic pressure by the propulsion system to the launcher’s payload and causing numerous of stress and constraints. Knowing the capabilities of the chamber be able to stretch its characteristic thru analysis and calculation. Reverberation time, Tr has been completed by integrated impulse response method. Additional analysis for repeatability measurement can be performed in order to know the exact value for each central frequency Tr. For the chamber diffusivity, number of acoustic mode, frequency response, and natural resonance frequency (MAXTIQ) has been defined. In succession to have sufficient analysis on total spread of frequency spectrum, the modal density, MD and modal analysis, MS has been included. Results shown that chamber can fulfilled in providing the reverberation acoustic test. Most of the chamber resonance cater at least one mode in the half power band width of the test object. Lower frequencies is well covered eventhough it is limited characteristic. Based on the analysis the absorption coefficient are in reasonable arrangement and the calculated equivalent sound absorption area are none exceeds the maximum limit for a chamber volume of 999.5m3 . There is lessen absorption factor when the environment are totally dry air. ANGKASA’s RATF OASPL has the capability to meet the maximum 155dB requirement. Further analysis is suggested with different arrangement of OASPL in the chamber for pattern evaluation.

KEYWORDS: Characterization, Acoustic, Frequency Response, Noise, Diffusivity, Absorption

REFERENCES:

[1] A.W. Mayne: The specification of large reverberant acoustic test facility, Journal of the IEST, Vol 52, Number 2 (2009)

[2] Launay, A; Tadoa Sakita, M.;Kim, Young0key K., “Comparison of Two High Intensity Acoustic Test Facilities”, (ESA SP-558, June 2004)

[3] N. H. T. Ahmad, N. Salim, A.A Tan, S. A. Ibrahim: High-intensity Acoustic Chamber System Spectrum Profiling for Sateliite Launching Environment (ICEPEA, Malaysia 2014)

[4] F. W. Grosveld: Characterization of the Reverberation Chamber at the NASA Langley Structural Acoustics Loads and Transmission (SALT) Facility (2013)

[5] N. Salim, N. H. Tauhid Ahmad, A.A Tan, S. A. Ibrahim: Reverberation Time Measurement for ANGKASA’s High Intensity Acoustic Chamber (ICEPEA, Malaysia 2014)

[6] A.A Tan, N. Salim, N. H. Tauhid Ahmad, S. A. Ibrahim: Reverberation Acoustic Chamber Simulation Characteristic Analysis (ICSANE, Malaysia 2014)

[7] Scott R. Foster, “Optimizing Room Size/Mode Calculation”, 2008

[8] David A. Bies, Colin H. Hansen, “Engineering Noise Control: Theory and Practice, 2009

[9] D. Monastero, P. Fagerman, E.R. Samuel: Reverberation Acoustic Test Facility Acceptance Test Plan, Doc NO. A10009, Ver.6 (2013)

[10] ISO International Standards, Acoustics – Measurement of Sound Absorption in a Reverberation Room. ISO 354:2003 Second Edition.International Organization for Standardization,Geneve, 2003.

[11] ISO International Standards, Acoustics – Attenuation of Sound during Propoagation Outdoors – Part 1: calculation of the absorption of sound by the atmosphere. ISO 9613-1:1993, First Edition. International Organization for Standardization,Geneve, 1993.

[12] J.S Lamancusa, “Engineering Noise Control” Penn State, 2009.

[13] D. Havelock,S. Kuwano,M. Vorlander,“Handbook of Signal Processing in Acoustics”,Vol.1 2008.

[14] A. Grewal, R. Ramakrishnan, W.O. Hughes, B.Woyski,G. Elfstrom, C. Mech: High Intensity Noise Generation for Extremely Large Reverberant Room Test Applications, Conference Proceedings of the Society for Experimental Mechanics Series, pp 103-118 (2011)

[15] Richard. H. Bolt, “Note on the normal frequency statistics in rectangular rooms”, J.Acoust.Soc.Am. 18(1) 130-133. (1946)