ok, so the guy from DSP emailed me this document about noise levels etc.. it's pretty in depth, so here goes.. Apologies if it's too much for the thread, but I don't have a link for it.... only the original document
VEHICLE NOISEPRIVATE
Whatâs been done to reduce noise from vehicles?
By the early 1990âs the perceived noise level of individual heavy goods vehicles had been reduced by half (10dB(A)) in as many years.
The noise of the average family saloon had been reduced by 5-6dB(A) which meant that 3 modern saloons made less noise than a similar 1978 model.
Since 1996 all new vehicles have had to meet even more stringent noise standards before entering service.
The UK is participating in the United Nations Economic Commission for Europe (UNECE) Working Group on vehicle noise which is examining the scope for further noise reductions.
Requirements restricting the noise from tyres are being introduced in stages from 2002 in accordance with EU Directive 2001/43/EC.
To reduce noise generated by âbody rattleâ from heavy lorries a guide to best practice for operators and others was published in 2000.
Quieter road surfaces are being introduced.
A consultation paper âTowards a National Ambient Noise Strategyâ for England has been published. Noise from road transport will be an important consideration for any strategy.
Engine noise
Measures to reduce traffic noise include setting noise emission standards for new vehicles. Mandatory standards have been in place since 1968, and the introduction of a series of stricter limits at European level meant that by 1996 the maximum noise of individual vehicles had effectively been halved from the previous decade. Implementation of an EU directive in 1996 saw further reductions ranging from 3 dB(A) for passenger cars to 5 dB(A) for intermediate trucks. It is the responsibility of manufacturers to develop appropriate technologies necessary to meet the new standards. Overall, noise emission limits for cars have been tightened from 82 dB(A) in 1978 to the current 74 dB(A), and from 91 dB(A) to 80 dB(A) for large buses and lorries during the same period. Further details are given in the Table below.
Reductions in noise levels brought by vehicle standards will continue, as new vehicles enter the fleet. This will be particularly beneficial in urban areas where the main source of noise from vehicles is the mechanical operation of the vehicle rather than contact between road surface and tyres. As indicated below, requirements restricting the noise from tyres will be introduced in stages from 2002 and further measures in this area are to be discussed.
Further progress in reducing mechanical noise at source has been restricted by the nature of the current EU type approval test procedure. A UNECE (United Nations Economic Commission for Europe) working group, in which the UK is participating, is currently examining the scope for establishing a new test procedure that would improve the correlation with vehicle use on the road. This work is expected to take a further 12-24 months. Once this is completed the EU Commission will consider whether it is able to make a new proposal to reduce mechanical noise from vehicles.
There is also continuing research and development being conducted in both the UK and Europe into quieter road surfaces and noise barriers through the use of porous asphalt and other quiet road surfacing materials. Further details are given below.
Table of past and present noise limit values
| PRIVATE Vehicle Category | Limits in 1978
dB(A) | Limits since October 1996
DB(A) | Overall reduction 1978 to 1996 |
| Passenger Cars | 82 | 74 | 8 dB(A) |
Large Buses & Coaches -
- engine < 150kW:
- engine ⥠150kW: | 89 | 78
80 | 11 dB(A)
9 dB(A) |
Small Buses & Light goods vehicles -
- GVW ⤠2t:
- 2 < GVW ⤠3.5t: |
84/85 |
76
77 |
8/9 dB(A)
7/8 dB(A) |
Heavy Goods -
- engine < 75kW:
- 75 ⤠engine < 150kW:
- engine ⥠150kW: | 89 | 77
78
80 | 12 dB(A)
11 dB(A)
9 dB(A) |
Tyre noise
Tyre noise is the noise generated by tyres when in motion. Studies have shown that noise generated by the tyreâroad sources are a significant environmental nuisance. The contribution of tyre noise to total vehicle noise becomes more significant as vehicle speed increases. To address this problem the EU has agreed a directive (2001/43/EC) which prescribes noise limits to be met by all newly designed tyres to be fitted to new vehicles from 2002. Most types of new tyres will have to meet these standards from 2009. The measure will remove some of the noisiest tyres from the market and will set a benchmark which will prevent new tyre designs from compromising tyre noise quality. The directive also contains a requirement for a tyre grip test procedure to be introduced within a specified timescale to ensure that safety characteristics are maintained when noise requirements are met.
âBody Rattleâ
Body rattle is the noise generated by metal to metal impact of parts of the body of heavy vehicles and the chassis. It includes noise generated by suspension systems, tipper bodies, lifting or tipping gear and loose tools and chains as well as body panel vibration. In response to concerns about this source of noise â which is not covered by any legal standards â an advisory group was set up to investigate the sources and magnitude of body noise and to develop a guide to the best practice for controlling this type of noise nuisance. The Guide, published in 2000, (ISBN 1 85112 434 9) describes the various design, maintenance or operator awareness issues that need to be considered in order to control these noise sources.
Road surfaces.
In 1998 the Government announced that whenever a trunk road in England needs to be resurfaced, the most appropriate noise reducing surface would be used in areas where noise was a particular concern. In addition, quieter road surfaces would be used as a matter of course for all new trunk road contracts. In 2000, the Ten-Year Plan for Transport pledged that over 60% of the trunk road network will be overlaid with quieter surfaces; this would include all sections having concrete surfaces, which are perceived to be particularly noisy.
The Highways Agency is developing a programme to accelerate the resurfacing of concrete roads. A quieter form of concrete surface (whisper concrete) was developed as an alternative to new lower noise asphalt materials, but the latter have proved to be more cost-effective. Industry has made significant advances in the technology of producing and laying these new quieter surfacing materials.
A regime (Highway Authorities Product Approval System) has been developed to assess the performance of materials for durability, skidding resistance and other engineering parameters as well as their potential to reduce noise. They are widely used by local highway authorities because of the range of HAPAS rated products now available.
Where residents are particularly concerned about noise from existing trunk roads and re-surfacing cannot be justified on normal maintenance grounds, alternative measures such as noise barriers are being considered. A ring-fenced budget of £5 million per year is being provided for action in the worst and most pressing cases, determined by criteria based on the predicted level and relative increase in the noise at the roadside. A list of locations meeting the criteria was published in 1999 and the Ten-Year Plan anticipates that action will have been taken at these locations to alleviate the effect of traffic noise by one means or another within the plan period.
Ambient noise strategy
Ambient noise (sometimes called environmental noise) is unwanted or harmful noise emitted by road, rail and air transport, and industrial activity. In November 2001 the Department for Environment, Food and Rural Affairs published a consultation paper âTowards a National Ambient Noise Strategyâ for England. For further information on the consultation see HYPERLINK
http://www.defra.gov.uk/environment/noise/ www.defra.gov.uk/environment/noise/. The consultation on the National Ambient Noise Strategy covers England only, and responsibility for noise policy in Scotland, Wales and Northern Ireland is with the relevant devolved administrations. Road transport is a major source of ambient noise in the UK, and will be an important consideration for any strategy. Already the Mayor of London had published a draft ambient noise strategy for London, which contains proposals for dealing with traffic noise specifically in the capital. Details of this can be found at HYPERLINK
London.gov.uk - Greater London Authority, Mayor of London, London Assembly London.gov.uk - Greater London Authority, Mayor of London, London Assembly.
ANNEX
Noise Units
For regulatory purposes vehicle noise is measured in terms of sound pressure level in decibels. The decibel scale is a logarithmic, rather than a linear progression. In practice, since the ear also responds in different degrees to sounds at different frequencies, sound pressure level measuring instruments usually apply the so called âAâ weighting which best represents the frequency response of the human ear. Noise measurement levels made in this manner are denoted as dB(A).
A logarithmic unit can be applied to any physical measurement (in the case of noise, sound pressure measured in Pascals) that needs to be expressed conveniently both in very small and very large quantities. It is the ratio of the measured quantity to an arbitrarily fixed level, expressed logarithmically. The decibel scale for sound pressure level uses 20μPa (20 x 10[SUP]-6[/SUP] Pa) as its point of reference since this is nominal sound pressure that can just be detected by the human ear, i.e. 20μPa = 0dB. In actual fact the decibel level is twenty times the logarithm of the ratio of the pressure level to 20μPa. The absolute Sound Pressure Level (SPL) in dB of a sound pressure P (in Pa) can therefore be calculated as follows:
SPL in dB = 20 x Log[SUB]10[/SUB] (P/20x10[SUP]-6[/SUP])
A change in noise level from one SPL to another can be expressed in dB as follows;
Change in SPL in dB = 20 x Log[SUB]10[/SUB] (P[SUB]new[/SUB]/P[SUB]old[/SUB])
Although a personâs perception of sound is of course subjective, it is generally recognised that a 3 decibel change in sound pressure level on the âAâ weighted scale (i.e. 3dB(A)) is the minimum change that may be perceptible to most people (see Table below). A change of 6dB(A) would be clearly noticeable while, as a general rule of thumb, a change of 10dB(A) would be twice as loud (or half as loud for a 10 dB(A) decrease).
| Approximate Increase in Sound Pressure (Pa) | Change in Sound Pressure Level
(dB) | Change in subjective loudness |
| x 1.4 | 3 | Just Perceptible |
| x 2 | 6 | Clearly Noticeable |
| x 3 | 10 | Twice as Loud |
| x 10 | 20 | Much Louder |
Sometimes noise levels are expressed in different ways e.g. in terms of sound power. This is also measured on a logarithmic scale, but in terms of sound power in Watts (W) relative to a level of 1 x 10[SUP]-12[/SUP] W. The Sound Power Level in dB of a power
L[SUB]w[/SUB] (in W) is calculated as follows;
Sound Power Level in dB = 10 x Log[SUB]10[/SUB] (
L[SUB]w[/SUB] /1 x 10[SUP]-12[/SUP])
Change in Sound Power dB = 10 x Log[SUB]10[/SUB] (
L[SUB]w[/SUB][SUB]new[/SUB]/
L[SUB]w[/SUB][SUB]old[/SUB])
This measurement is useful in attempting to estimate the number of new vehicles it would take to produce the same level of noise as an old vehicle. For instance it is generally held that it would take 7 modern cars to produce the noise of one 1970âs car. This statement is based on an 8dB noise reduction (the reduction in maximum permitted decibel limits for passenger cars during this time), equating to a reduction to approximately one seventh of the original sound power.
Warning: Although Sound Pressure Level and Sound Power Level are both measured on a decibel scale from 0dB (threshold of audibility) to 120dB (upper limit of non-painful sound) and beyond, the measurements are not strictly analogous. For example a change in Sound Pressure Level of 40dB does not necessarily correspond to a change in Sound Power Level of 40dB. However, if all other variables (e.g. distance from noise source) remain unchanged, it is possible to calculate proportional change in Sound Power Level from a change in dB Sound Pressure Level.
See Annex for description of noise unit measurement.
Worked Example
The car noise limit reduced from 82dB(A) in the 1970s to 74dB(A) in the 1990s.
Change in noise level (old to new) = -8 dB(A)
Ratio of new to current sound power = Log[SUB]10[/SUB][SUP]-1[/SUP] (-8/10)
= 0.158
The new car produces 15.8% of the sound power of the old car, or in other words, it would take approximately 6.3 modern cars to produce the noise of a 1970âs car.
To the human ear the 8dB(A) change in noise level represents a noticeable decrease in loudness but not as much as a halving of the loudness (which would require a change of about 10dB(A)).
They're still coming back to me tomorrow with the exact up-to-date type approved dba rating for the RS3 and also the distances, speeds rpm etc!
so I'm no good for a group buy just yet..
