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Noise Characteristics of Eight Helicopters.

ADA043842

Publication Date	1977
Personal Author	True, H. C.; Rickley, E. J.
Page Count	172
Abstract	This report describes the noise characteristics of eight Helicopters during level flyovers, simulated approaches, and hover. The data were obtained during an FAA/DOT Helicopter Noise Program to acquire a data base for possible helicopter noise regulatory action. The helicopter models tested were the Bell 47G, 206L, and 212 (UHIN), the Hughes 300C and 500C, the Sikorsky S-61 (SH-3B) and S-64 (CH-54B) and the Vertol CH-47C. The acoustic data is presented as Effective Perceived Noise Level, A-weighted sound pressure level and 1/3 octave band sound pressure level with a slow meter characteristic per FAR Part 36. Selected waveforms and narrow band spectra are also shown. Proposed methods to quantify impulsive noise ('blade slap') are evaluated for a level flyover for each of the Helicopters. The tested helicopters can be grouped into classes depending upon where the maximum noise occurs during a level flyover. Helicopters with the higher main rotor tip speeds propagate highly impulsive noise ahead of the helicopter. The maximum noise for most of the helicopters occurs near the overhead position and appears to originate from the tail rotor. Unmuffled reciprocating engine helicopters appear to have significant engine noise behind the helicopter. Noise levels, when compared as a function of gross weight and flown at airspeeds to minimize 'compressibility slap' form a band 7 EPNdB wide with a slope directly proportional to gross weight. The quieter helicopters have multibladed rotors and tipspeeds below 700 fps.
Keywords	Aircraft noise Helicopters Acoustic signatures Rotor blades Tail rotors Measurement Approach Hovering Flight Helicopter noise Flyovers Bell 47G Aircraft Bell 206L Aircraft Bell 212 Aircraft Hughes 300C Aircraft Highes 500C Aircraft SH-3B Aircraft CH-54B Aircraft CH-47C Aircraft Impulsive noise
Source Agency	Non Paid ADAS Department of Transportation Federal Aviation Administration
NTIS Subject Category	51C - Aircraft 68B - Noise Pollution & Control
Corporate Authors	Federal Aviation Administration Washington D C Systems Research and Development Service
Document Type	Technical Report
Title Note	Final rept.
NTIS Issue Number	197723

Noise Characteristics of Eight Helicopters.

Noise Characteristics of Eight Helicopters.
ADA043842

Publication Date	1977
Personal Author	True, H. C.; Rickley, E. J.
Page Count	172
Abstract	This report describes the noise characteristics of eight Helicopters during level flyovers, simulated approaches, and hover. The data were obtained during an FAA/DOT Helicopter Noise Program to acquire a data base for possible helicopter noise regulatory action. The helicopter models tested were the Bell 47G, 206L, and 212 (UHIN), the Hughes 300C and 500C, the Sikorsky S-61 (SH-3B) and S-64 (CH-54B) and the Vertol CH-47C. The acoustic data is presented as Effective Perceived Noise Level, A-weighted sound pressure level and 1/3 octave band sound pressure level with a slow meter characteristic per FAR Part 36. Selected waveforms and narrow band spectra are also shown. Proposed methods to quantify impulsive noise ('blade slap') are evaluated for a level flyover for each of the Helicopters. The tested helicopters can be grouped into classes depending upon where the maximum noise occurs during a level flyover. Helicopters with the higher main rotor tip speeds propagate highly impulsive noise ahead of the helicopter. The maximum noise for most of the helicopters occurs near the overhead position and appears to originate from the tail rotor. Unmuffled reciprocating engine helicopters appear to have significant engine noise behind the helicopter. Noise levels, when compared as a function of gross weight and flown at airspeeds to minimize 'compressibility slap' form a band 7 EPNdB wide with a slope directly proportional to gross weight. The quieter helicopters have multibladed rotors and tipspeeds below 700 fps.
Keywords	Aircraft noise Helicopters Acoustic signatures Rotor blades Tail rotors Measurement Approach Hovering Flight Helicopter noise Flyovers Bell 47G Aircraft Bell 206L Aircraft Bell 212 Aircraft Hughes 300C Aircraft Highes 500C Aircraft SH-3B Aircraft CH-54B Aircraft CH-47C Aircraft Impulsive noise
Source Agency	Non Paid ADAS Department of Transportation Federal Aviation Administration
NTIS Subject Category	51C - Aircraft 68B - Noise Pollution & Control
Corporate Authors	Federal Aviation Administration Washington D C Systems Research and Development Service
Document Type	Technical Report
Title Note	Final rept.
NTIS Issue Number	197723