Interfering noise
From Wikipedia, the free encyclopedia
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 as unpleasant, disturbing and interfering. This sound event usually releases negative associations as regards the suitability of the product and it is on the whole perceived as not matching the product.
Contents |
[edit] Definition
A noise can be characterised as interfering, if it fulfils at least one of the 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 definition of sound quality. The definition considers the psychologically important distinction between disturbing and function sounds. Function sounds are sounds such as the often desired full sound of an engine. In addition, there is trend in the automotive industry that a complete acoustic insulation is not desirable from the point of view of the customer.
[edit] 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 bodies
A cause of interfering sounds occurring predominantly in the car interior is the relative motion of different construction parts to each other. Motion is usually caused by the vibration of the car when driving. Interference sound develops at contact points. If two parts touch one another or rub against each other, then interference sound can develop. Therefore the search for the core causes of interfering sounds is closely related to the search for relevant contact points. All critical contact points can be isolated and marked on the basis of factors such as previous experience, surveys by quality-specialists from car manufacturing and surveys by specialists of interference acoustics. Here, additionally, construction designs, pictures, drafts (and whatever is otherwise available) are used, in order to represent the problem visually. Videos from previous experience are particularly important thereby because they address the audiovisual part of the human brain and are therefore particularly efficient to make specialists aware of problems.
[edit] 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 is comparatively 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, can then become the problem. It is thus the human mind and not the hearing, which decides whether a noise is felt as disturbing or pleasant. The human hearing can rather be seen as registering the pressure waves and frequencies of sound just like a physical measuring instrument. Stick-slip noises rank first in the hit-list of the most interfering sounds. Examples are sounds such as squeaking, creaking and grinding sounds.
[edit] 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
