A Way to Measure Aircraft Noise, to Discriminate Among ... TRB10.pdf · A Way to Measure Aircraft Noise, to Discriminate Among Ground and Air Sources, ... Recall and analyze data

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

mailto:[email protected]�


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


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


Measuring microphone and windscreen

All-weather Windscreen Structure

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

Wind noise Reduction-WS-13

10m/s=22mph

22 MPH


Measurement site

NA-37 placed in a cubicleMicrophones

placed in a roof

Communication control, application software


The microphone array


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


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


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

Identification


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


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


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


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


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


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



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



Characteristics of noise direction

Time Histories

-150

-100

-50

0

50

100

150

200

250

300

350

Time

Time

Degr

ees Automobile

AircraftAircraft


Detection of wind noiseAircraft noise Wind noise

Wind noise is detected in random direction.

Wind noise is identified from the degree of randomness


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


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



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


Measurement site

Measurement site

Runway

16L・R/34L・R

Runway

02/20

Helicopter：H

Aircraft

like B747, B767, B777,

A300, A320


B767 and Helicopter

Outdoor microphone and microphones for identification with radar reception antenna

View of measurement site


B747 34L L/D Helicopter 02 L/D

Automobile


Two objects found in the event

（Helicopter to B747）Integrated noise of automobile and aircraft found

（Automobile to A300）

Data taken by acoustic method


Information from RF method


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.


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


Questions?

Documents

A Way to Measure Aircraft Noise, to Discriminate Among ... TRB10.pdf · A Way to Measure Aircraft Noise, to Discriminate Among Ground and Air Sources, ... Recall and analyze data