Interfering noise

Interfering noises(or interfering sounds) are sounds with a negative sound quality, that is,the sound event leads to a hearing event, which is perceived asunpleasant, disturbing and interfering. This sound event usuallyreleases negative associations as regards the suitability of theproduct and it is on the whole perceived as not matching the product.

Definition

A noise can be characterised as interfering, if it fulfils at least one ofthe following conditions:
*A sound is unpleasant or interfering, even if passengers expect this sound due to their actions. The sound quality is worse than expected. The extent to which the person feels disturbed (little or high) is not relevant.
*A sound occurs without the user expecting the sound event (e.g. rattling of parts of the interior trims).
*The noise does not occur due to any event related to the usage of the automobile (e.g. warning noises due to a lack of engine lubrication).

There is a multiplicity of parameters which play a role in the definitionof sound quality. The definition considers the psychologicallyimportant distinction between disturbing and function sounds.Function sounds are sounds such as the often desired full sound ofan engine. In addition, there is trend in the automotive industry thata complete acoustic insulation is not desirable from the point of viewof the customer.

Emergence of interfering noises

Interfering noises are a result of a relative motion at contact points. For the occurrence of interfering sounds two conditions must be fulfilled together:
* a contact between bodies and
* relative motion between bodiesA cause of interfering sounds occurring predominantly in the carinterior is the relative motion of different construction parts to eachother. Motion is usually caused by the vibration of the car whendriving. Interference sound develops at contact points. If two parts touch one another or rub against each other, theninterference sound can develop. Therefore the search for the corecauses of interfering sounds is closely related to the search forrelevant contact points.All critical contact points can be isolated and marked on the basis offactors such as previous experience, surveys by quality-specialistsfrom car manufacturing and surveys by specialists of interferenceacoustics. Here, additionally, construction designs, pictures, drafts (andwhatever is otherwise available) are used, in order to represent theproblem visually. Videos from previous experience are particularlyimportant thereby because they address the audiovisual part of thehuman brain and are therefore particularly efficient to makespecialists aware of problems.

Characterization of the interfering noise level

An interfering noise doesn't necessarily have to be loud.A mosquito can produce considerable disturbing sound, although it iscomparatively quiet with a volume of only approx. 30 dB(A). An orchestra, by contrast, might producen very pleasant sounds, even if its volume amounts to nearly 90 dB(A). The final of an opera can be just as loud as heavy motorway noise. People differentiates unconsciously between good and bad sounds.Each sound signals a message, which, if perceived as disturbing, canthen become the problem. It is thus the human mind and not thehearing, which decides whether a noise is felt as disturbing orpleasant.The human hearing can rather be seen as registering the pressurewaves and frequencies of sound just like a physical measuringinstrument.Stick-slip noises rank first in the hit-list of the most interferingsounds. Examples are sounds such as squeaking, creaking andgrinding sounds.

Further reading

* Klaus F. Steinberg: "With all senses, The first book on how to eliminate interfering sound in the car". wjr-verlag, Februar 2007, ISBN 3-935659-62-8

External links

* http://www.acip.biz/index.html