Interfering noises are noises with negative noise quality, that is, the sound event leads to an auditory event that is perceived as unpleasant, annoying, disruptive, triggering negative associations or not suitable for the product.
It is a sound ( . Engl interfering noise) then referred to as noise, when at least one of the following conditions is met:
- A noise is uncomfortable or annoying even if a person expects a noise based on what he is doing. The sound quality is worse than expected. The degree of disturbance (low or high) is not relevant.
- A noise occurs without the user being able to expect the noise event through his or her actions (for example rattling of interior panels).
- The noise is not an information carrier in the sense of user guidance (e.g. warning noise in the event of insufficient engine lubrication).
A large number of different parameters go into determining the sound quality. The definition takes into account the psychologically important distinction between interference and functional noises. Functional noises such as a rich engine sound are definitely desirable. There is also agreement among the automotive developers that complete acoustic insulation is not desired by the customer.
Interfering noises are caused by relative movement at contact points. Two conditions must be met in order for background noise to arise:
- The contact between bodies
- Relative movement between bodies
The cause of these noises, which mostly act in the interior, is the relative movement of various components to one another, which is triggered by the vibrations while driving. Interfering noises arise at contact points. If two parts hit each other or rub against each other, this can cause interference. The search for the root causes of background noise is therefore closely linked to the search for relevant contact points. On the basis of previous experience from previous products, on the basis of further interviews with quality specialists from production, on the basis of interviews with noise specialists and on the basis of our own knowledge, all critical contact points can now be isolated and marked. In addition, construction drawings, pictures, hand sketches (and whatever else is available) are used to visualize the problem. Videos from previous experiences are particularly important because they address the audiovisual part of the human brain and are therefore particularly efficient in generating problem awareness.
Characterization of the background noise level
Noise does not have to be loud. A mosquito in a bedroom can produce an annoying noise, even though it is very quiet and only around 30 dB (A) . In contrast, an orchestra can (but does not have to) produce very pleasant sounds, even if they are close to 90 dB (A). The finale of a Wagner opera can be just as loud as motorway noise. But everyone unconsciously differentiates between good and bad sounds. Every sound signals a certain message to the subconscious. If it is unwelcome it can become a problem. So it is the brain and not the ear that decides whether a sound is perceived as pleasant. The human hearing apparatus only registers pressure waves and frequencies of sound like a physical measuring device . Stick-slip noises ( stick-slip noises) such as squeaking, creaking and creaking are right at the top of the hit list of the most annoying noises .
- Klaus F. Steinberg: With all senses, The big book of Störgerärmakustik . copy-us, August 2004, ISBN 3-935861-09-5
- Klaus F. Steinberg: With all senses, The first book on how to eliminate interfering sound in the car . wjr-verlag, February 2007, ISBN 3-935659-62-8