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Noise is generally defined as unwanted sound that can be unpleasant or even harmful to humans. Sound consists of frequency (pitch) and sound pressure (loudness) and is measured in dB(A). Whether sound is perceived as noise depends not only on the type of sound, but also on personal perception. This makes it difficult to evaluate noise objectively. For this reason, noise has often been perceived as a health and environmental problem only to a limited extent in the past and is still frequently underestimated today.
Differences in volume are often only noticeable at a level difference of 3 dB(A). However, recent studies show that differences of 1 dB(A) can already be perceived.
That depends on the design and condition of the windows. Soundproof windows can greatly reduce noise, but are only fully effective when closed. If a soundproof window is tilted, the external noise entering the room can be reduced by around 15-20 dB(A).
When two sounds of equal loudness come together, the overall loudness only increases by 3 dB(A). This is due to the way we measure sound. Doubling the noise source (e.g. twice as many cars) increases the noise level by 3 dB(A) ( ). This does not mean that the noise level doubles or that the noise is perceived as twice as loud.
Further explanation:
The human ear has a very wide range of hearing. If this were to be physically represented and measured correctly as sound pressure (in pascals), the values would range from 0.00002 to around 20 pascals. This is very impractical. For this reason, a logarithmic representation adapted to humans (in the unit decibel: dB(A)) is used, which leads to unusual calculation rules.
For example, two sound sources with the same loudness, each at 60 dB(A), together are only 63 dB(A) loud. So 60 dB(A) + 60 dB(A) = 63 dB(A). This also means that a noise level increases by 3 dB(A) if, for example, the traffic on a road doubles.
When the noise level increases by 10 dB(A), it sounds twice as loud to us. For example, a street with 75 dB(A) is perceived as twice as loud as one with 65 dB(A). When the level drops by 10 dB(A), the noise is only perceived as half as loud.