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GB2036323A - Noise measurement - Google Patents

Noise measurement Download PDF

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Publication number
GB2036323A
GB2036323A GB7939561A GB7939561A GB2036323A GB 2036323 A GB2036323 A GB 2036323A GB 7939561 A GB7939561 A GB 7939561A GB 7939561 A GB7939561 A GB 7939561A GB 2036323 A GB2036323 A GB 2036323A
Authority
GB
United Kingdom
Prior art keywords
noise
ground
meter
measurement
hemisphere
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
GB7939561A
Other versions
GB2036323B (en
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
SECR DEFENCE
UK Secretary of State for Defence
Original Assignee
SECR DEFENCE
UK Secretary of State for Defence
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by SECR DEFENCE, UK Secretary of State for Defence filed Critical SECR DEFENCE
Priority to GB7939561A priority Critical patent/GB2036323B/en
Publication of GB2036323A publication Critical patent/GB2036323A/en
Application granted granted Critical
Publication of GB2036323B publication Critical patent/GB2036323B/en
Expired legal-status Critical Current

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Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01H—MEASUREMENT OF MECHANICAL VIBRATIONS OR ULTRASONIC, SONIC OR INFRASONIC WAVES
    • G01H3/00—Measuring characteristics of vibrations by using a detector in a fluid

Landscapes

  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Measurement Of Mechanical Vibrations Or Ultrasonic Waves (AREA)

Abstract

A method of noise measurement includes the step of mounting a noise meter on an apex of a body, in the form of a segment of a sphere or in a similar form, having a base which rests on the ground. The body prevents ground-reflected noise from reaching the meter.

Description

SPECIFICATION Improvement in methods of noise measurement The present invention relates to methods of noise testing.
The problem of noise is currently of great importance and many countries are introducing, or have introduced, legislation regarding maximum permissible noise levels. The most publicised legislation regards air transport noise, but other sources include vehicular traffic and industrial noise. However, for successful implementation of a noise policy it must be possible to measure accflYately the noise emanating from a source, and current methods of noise measurement are proving to be unsatisfactory. For example, regulations regarding air traffic noise stipulate that measurements should be made with a noise meter positioned 1.2 m above ground level.With a noise -meter in such a position (or indeed at any position above the ground) noise reaches the meter not only directly from the source, but after reflection from the ground, and this causes an interference effect which distorts the measured noise spectrum. Positioning the noise meter directly on the ground is no answer, as results are affected by the nature of the ground. It has been suggested that measurements should be made with the noise meter placed on a reflector board lying on the ground, which should theoretically give a noise measurement 6 dB greater than the true free field noise level. It has been found, however, that the size of any gaps between the board and the ground on which it is resting are critical and also that readings can be affected by noise diffraction round the edges of the board.
The present invention provides a method of noise measurement which gives a true noise spectrum.
According to the present invention a method of noise measurement includes the step of flush mounting a noise meter on an apex of a body, in the form of a segment of a sphere which is at least a hemisphere, or in a similar form, having a base which rests on the ground.
An example of a similar body is a hemiellipsoid.
The segment is preferably hollow for ease of handling, and must be formed from an acoustically hard material. A suitable material is fibreglass.
Noise measurement apparatus for carrying out the invention is illustrated in the accompanying drawing. A hollow glass fibre hemisphere 10 resting on ground 11 has a noise meter 12 flush mounted at its apex. Noise arriving at the meter 12 from a noise source 1 3 does so only directly, noise reflected from the ground 11 being deflected away from the meter 12 by the surface of the body 10.
The size of the hemisphere 10 will depend on the frequency of the noise which is being measured. As an example, when the range of frequencies of interest is between 500 Hz and 20 kHz a sphere having a diameter of 3 ft will be required, whilst a 6 ft diameter sphere will cope with a range of 250 Hz to 20 kHz.
1. A method of noise measurement including the step of flush mounting a noise meter on an apex of a body, in the form of a segment of a sphere which is at least a hemisphere, or in a similar form, having a base which rests on the ground.
2. A method of noise measurement as claimed in claim 1 wherein the body is in the form of a hemi-ellipsoid.
3. A method of noise measurement as claimed in claim 1, for measuring noise having a lowest frequency of 500 Hz wherein the body is a hemisphere having a diameter of the order of three feet.
4. A method of noise measurement as claimed in claim 1, for measuring noise having a lowest frequency of 250 Hz, wherein the body is a hemisphere having a diameter of the order of six feet.
5. A method of noise measurement as claimed in any one of claims 1 to 4 wherein the body is hollow.
6. A method of noise measurement as claimed in any one of claims 1 to 5 wherein the body is made of glass fibre.
7. A method of noise measurement substantially as herein described with reference to the accompanying drawing.
8. Apparatus for measuring noise by a method as claimed in any one of claims 1 to 7.
**WARNING** end of DESC field may overlap start of CLMS **.

Claims (8)

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Improvement in methods of noise measurement The present invention relates to methods of noise testing. The problem of noise is currently of great importance and many countries are introducing, or have introduced, legislation regarding maximum permissible noise levels. The most publicised legislation regards air transport noise, but other sources include vehicular traffic and industrial noise. However, for successful implementation of a noise policy it must be possible to measure accflYately the noise emanating from a source, and current methods of noise measurement are proving to be unsatisfactory. For example, regulations regarding air traffic noise stipulate that measurements should be made with a noise meter positioned 1.2 m above ground level.With a noise -meter in such a position (or indeed at any position above the ground) noise reaches the meter not only directly from the source, but after reflection from the ground, and this causes an interference effect which distorts the measured noise spectrum. Positioning the noise meter directly on the ground is no answer, as results are affected by the nature of the ground. It has been suggested that measurements should be made with the noise meter placed on a reflector board lying on the ground, which should theoretically give a noise measurement 6 dB greater than the true free field noise level. It has been found, however, that the size of any gaps between the board and the ground on which it is resting are critical and also that readings can be affected by noise diffraction round the edges of the board. The present invention provides a method of noise measurement which gives a true noise spectrum. According to the present invention a method of noise measurement includes the step of flush mounting a noise meter on an apex of a body, in the form of a segment of a sphere which is at least a hemisphere, or in a similar form, having a base which rests on the ground. An example of a similar body is a hemiellipsoid. The segment is preferably hollow for ease of handling, and must be formed from an acoustically hard material. A suitable material is fibreglass. Noise measurement apparatus for carrying out the invention is illustrated in the accompanying drawing. A hollow glass fibre hemisphere 10 resting on ground 11 has a noise meter 12 flush mounted at its apex. Noise arriving at the meter 12 from a noise source 1 3 does so only directly, noise reflected from the ground 11 being deflected away from the meter 12 by the surface of the body 10. The size of the hemisphere 10 will depend on the frequency of the noise which is being measured. As an example, when the range of frequencies of interest is between 500 Hz and 20 kHz a sphere having a diameter of 3 ft will be required, whilst a 6 ft diameter sphere will cope with a range of 250 Hz to 20 kHz. CLAIMS
1. A method of noise measurement including the step of flush mounting a noise meter on an apex of a body, in the form of a segment of a sphere which is at least a hemisphere, or in a similar form, having a base which rests on the ground.
2. A method of noise measurement as claimed in claim 1 wherein the body is in the form of a hemi-ellipsoid.
3. A method of noise measurement as claimed in claim 1, for measuring noise having a lowest frequency of 500 Hz wherein the body is a hemisphere having a diameter of the order of three feet.
4. A method of noise measurement as claimed in claim 1, for measuring noise having a lowest frequency of 250 Hz, wherein the body is a hemisphere having a diameter of the order of six feet.
5. A method of noise measurement as claimed in any one of claims 1 to 4 wherein the body is hollow.
6. A method of noise measurement as claimed in any one of claims 1 to 5 wherein the body is made of glass fibre.
7. A method of noise measurement substantially as herein described with reference to the accompanying drawing.
8. Apparatus for measuring noise by a method as claimed in any one of claims 1 to 7.
GB7939561A 1978-11-20 1979-11-15 Noise measurement Expired GB2036323B (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
GB7939561A GB2036323B (en) 1978-11-20 1979-11-15 Noise measurement

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB7845181 1978-11-20
GB7939561A GB2036323B (en) 1978-11-20 1979-11-15 Noise measurement

Publications (2)

Publication Number Publication Date
GB2036323A true GB2036323A (en) 1980-06-25
GB2036323B GB2036323B (en) 1983-03-02

Family

ID=26269657

Family Applications (1)

Application Number Title Priority Date Filing Date
GB7939561A Expired GB2036323B (en) 1978-11-20 1979-11-15 Noise measurement

Country Status (1)

Country Link
GB (1) GB2036323B (en)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE3213127A1 (en) 1982-04-08 1983-10-27 Deutsche Forschungs- und Versuchsanstalt für Luft- und Raumfahrt e.V., 5000 Köln Method for measuring the noise of rotating propellers during overflight by an aircraft

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE3213127A1 (en) 1982-04-08 1983-10-27 Deutsche Forschungs- und Versuchsanstalt für Luft- und Raumfahrt e.V., 5000 Köln Method for measuring the noise of rotating propellers during overflight by an aircraft

Also Published As

Publication number Publication date
GB2036323B (en) 1983-03-02

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PCNP Patent ceased through non-payment of renewal fee