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A Way to Measure Aircraft Noise, to Discriminate Among Ground and Air Sources, and to Identify Wind Generated Noise
Scantek, Inc.www.ScantekInc.com
Richard J. PeppinScantek, Inc.
410-290-7726 phone [email protected] www.ScantekInc.com
Scantek, Inc.www.ScantekInc.com
Introduction Discusses an acoustical instrument that
can be used for airports or for industrial sites measure a time history of sound level identify the nature of, and often the location
of, emitters to differentiate some sources even vehicles
and trains, and wind generated noise if used on the boundary of a factory, can
differentiate between sources on each side of the fence..
Environmental Noise Monitoring System
Used for Aircraft noise Road traffic noise Construction noise Rail yard and rail pass-by noise Factory noiseThe system allows you to Collect environmental noise data Store data as audio recording and Lp or Leq Recall and analyze data on site, or thru
internet
The System:
Environmental Noise Monitor Sound Level Meter Outdoor Microphone Set Environmental Noise Processing Program Noise Identification Unit (to detect a
direction from sound source)
Data Processing Environmental noise data processing
software
Scantek, Inc.www.ScantekInc.com
Basic meter
Measurement: 28-138 dBA
Noise floor about 10 dB lower
Class 1 Only Lp, not Leq Leq is calculated
Sound Level Meter NA-83 for NA-37 (1)
Compliant with IEC 61672-1 Class 1(with all-weather windscreen and microphone extension cable)
Periodic calibration just means removing a small unit.
Rain and wind resistant EMC shielded Remote calibration check
RION NA-37 Front Panel
Identification unit AN-37
GPS module
Sound level meter NA-83
Color LCD
Operation keys
Power switch
LAN
USB
RS-232-C
DC connector
Internal battery
AC connector
Radar input
Features
Automatically adjust clock Check data at measuring site Simultaneously Receive and log weather information Automatically record measuring coordinates Record and detect locations and directions
of sources
System Configuration-Example
Windows PCMicrophone systemNA-37 main body
GPS antenna
SSRreceiver
AN-37Identifier
NA-83 SLM
3 axismicrophone
MS-11
USBprinter
USBmemory
Online comm. Network
Overall Frequency Response
-4.0-3.5-3.0-2.5-2.0-1.5-1.0-0.50.00.51.01.52.02.53.03.54.0
10 100 1000 10000 100000Frequency [Hz]
Re
lati
ve
se
ns
itiv
ity
[d
B]
GREEN DOTTED- WITHOUT WINDSCREEN or COMPENSATION.RED- WITH WINDSCREEN but WITHOUT COMPENSATION.BLACK- WITH WINDSCREEN and COMPENSATION
Scantek, Inc.www.ScantekInc.com
Measurement site
NA-37 placed in a cubicleMicrophones
placed in a roof
Communication control, application software
Scantek, Inc.www.ScantekInc.com
Flowchart of aircraft noise identification by acoustical method
Noise events detected
Sound direction detected
Overhead noise identified
Wind noise identified
Direction of noise source detected
Result of identification displayed
Scantek, Inc.www.ScantekInc.com
Features
Aircraft Noise Identifier: acoustical method Sound direction detected by 3-axis microphone
system Detection microphone spacing is very small Connecting cables for microphones integrated into
one cable
Reliable identification results provided
Scantek, Inc.www.ScantekInc.com
Aircraft noise identification
3-axial microphones Radar inquiry signal from aircraft
Sound sources are identified using the both acoustic and RF method
Reliable information attached to noise events
Scantek, Inc.www.ScantekInc.com
Aircraft Noise Processing Program Detection and identification of noise events Noise event is detected by acoustic method at
first. Noise event is identified by RF methods Identify whether the noise event is made by
aircraft. When noise events are detected the data are
displayed simultaneously. Vector data about noise direction during the
events Radar identification data Sound recording file
Scantek, Inc.www.ScantekInc.com
Detection of possible Noise events
If noise is not beyond the trigger level and/or time period, it is recorded as possible noise event.
Trigger levelTrigger level not
reached
Recorded as Possible noise event
Based on measurements: set more suitable trigger level
Scantek, Inc.www.ScantekInc.com
Identification of overhead noise
90
0
Angle threshold,
x deg
deg
Angle component of noise direction
TimeTime period of noise event, b
Time period that it is beyond angle threshold, a
a/b≧y → Overhead noise
a/b<y → Ground noise
Scantek, Inc.www.ScantekInc.com
時間
time
Inquiry signal levels
Period of noise event
Calculation of
an averaged signal level
Identification of overhead noise
Calculates an averaged signal level during noise event
When above the threshold level, it is identified as aircraft noise
Averaged signal level ≧ threshold →Overhead noise
Averaged signal level<threshold →Ground noise
Scantek, Inc.www.ScantekInc.com
Principle:Two microphones gives the angle from the measurement site to sound source. From time difference between two microphones detecting the noise.
No time difference when noise arrives in right angle to the microphones
Waveform
Detection of noise direction
Scantek, Inc.www.ScantekInc.com
The angle θ is calculated from the time difference, t
When the same noise does not reach to two microphones at the same time, there is elevation angle from sound source to microphones.
θt
Waveform
Detection of noise direction
Scantek, Inc.www.ScantekInc.com
Two microphones on vertical line gives us an angle to noise source.
Four microphones gives us noise direction in three dimensions.
M2
M1
M3
M0
3軸方向識別装置
X 軸
Z 軸
Y 軸
θδ
Detection of noise direction
Scantek, Inc.www.ScantekInc.com
Characteristics of noise direction
Time Histories
-150
-100
-50
0
50
100
150
200
250
300
350
Time
Time
Degr
ees Automobile
AircraftAircraft
Scantek, Inc.www.ScantekInc.com
Detection of wind noiseAircraft noise Wind noise
Wind noise is detected in random direction.
Wind noise is identified from the degree of randomness
Scantek, Inc.www.ScantekInc.com
Aircraft noise identification by RF method Receipt of an identification
code from aircraft via SSR (secondary surveillance radar) radio signal
Strength/weakness of signal a measure of distance
SQUWAK allows identification of aircraft or not At different sites
Altitude determined Acoustic+ RF increases
accuracy of identification
Scantek, Inc.www.ScantekInc.com
Flowchart of aircraft noise identification
Identification result
by acoustic method
Integration of the both identification results
Identification result
by RF method
Final identification result
Detection of noise events
Scantek, Inc.www.ScantekInc.com
Site Measurement: several fight tracks
Sound source Large aircraft about 65 dB, 3000 feet Helicopter, small-size about 85 dB, 1000
feet Automobile, truck and crane
Measurement Automatically measured by NA-37 Manually measured by person
Scantek, Inc.www.ScantekInc.com
Measurement site
Measurement site
Runway
16L・R/34L・R
Runway
02/20
Helicopter:H
Aircraft
like B747, B767, B777,
A300, A320
Scantek, Inc.www.ScantekInc.com
B767 and Helicopter
Outdoor microphone and microphones for identification with radar reception antenna
View of measurement site
Scantek, Inc.www.ScantekInc.com
Two objects found in the event
(Helicopter to B747)Integrated noise of automobile and aircraft found
(Automobile to A300)
Data taken by acoustic method
Scantek, Inc.www.ScantekInc.com
After the measure
If it is difficult to measure aircraft noise, i.e. there are several runways close to roadways A noise event that aircraft noise was initially
identified as ground noise Eventually identified as aircraft noise by using RF
method.
Using the both acoustic and RF method make it possible to get the detail information from noise events.
Scantek, Inc.www.ScantekInc.com
Public Noise Disclosure Real-Time Information System
Information disclosure of noise data data at noise monitor is collected in real time, employed at vicinity of the airport
Instantaneous level data from all points are also collected
Terminals can be installed at locations such as city hall display of various kinds of information
Info can be modified over the Internet