Outside-inside difference in environmental noise levels

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Scope

What is the average a) instantaneous b) long-term difference in A-weighted sound levels of environmental noise, when measured outside and inside a residential building, taking into account window opening habits?

Note: The answers depend on a number of variables, such as a) spectral content (i.e. source) of the noise b) temporal distribution of the noise c) sound insulation of the facade(s) d) use of ventilation windows e) sound absorption inside the building f) position where the indoor noise is measured.

Thus, the ideal answer would be given as a function of each of these variables. However, for the purpose of this variable, approximate data (e.g. pertaining to typical conditions) is sufficient.

Definition

Data

WG-HSEA (2004). Position paper on dose-effect relationships for night time noise.

Ch. 3.4.3 Inside to outside

"An average level difference of 21 [dB] has been chosen, as this takes into account that even in well-insulated houses windows may be open a better part of the year... It should be stressed that this conversion is thought to be highly dependent on local building habits, climate and window behaviour."

Ch. 6.1 Inside / outside differences

"There are many types of window in the EU... The simplest types of facade have a sound reduction ... of usually less than 24 dB, and the most elaborated facades ... have sound reductions of more than 45 dB. In central Europe, most windows are of the double-pane (thermopane) type... Their range of sound reduction is between 30 and 35 dB when closed.

When night-time environmental noise reaches high levels, residents tend to close their bedroom windows. The two latter studies found that more than 50% of bedroom windows are closed when outside road traffic noise levels exceed 55 dB (LAeq). ... Schreckenberg et al (1999) report a much steeper increase in the incidence of closed windows when road 23 traffic noise reaches high levels of than is the case with increased levels of railway noise. Even when night-time noise levels reach 55 dB, only 35 % of the residents exposed to railway noise reported that they close their windows at night. It is remarkable that this finding is replicated in Sweden...

When windows are slightly open, outside sound levels are usually reduced by 10 – 15 dB. ... In Passchier-Vermeer [ref.] detailed noise measurements were carried out inside and outside the bedroom and at the same time window position was measured with sensors. The results showed that windows are fully closed in only in 25% of the nights. This results in average inside-outside differences of around 21 dB, with there being only a slight difference between single [21.3] and double-glazed [22.2] windows. ... Nevertheless, there was a large variation in insulation values.

It should be stressed that this figure only applies to facades that have not been fitted with special appliances to reduce noise impact."

EEA Technical report No 11-2010. Good practice guide on noise exposure and potential health effects

Annex II, ii. From outdoor levels to indoor exposure

"As the Lnight is an annual value, the insulation value is also to be expressed as such. ... The issue is complicated by the fact that closing behaviour is, to a certain extent, dependent on noise level. When data about effects are expressed with indoor noise levels (i.e. inside bedrooms) as the parameter, they need to be converted to Lnight, in accordance with the END definition. The most important assumption is the correction from inside levels to outside levels. ... In the EU‑position paper on night time noise a default insulation value of 21 dB was used. To convert to other insulation values, the following method should be used...:

Δ_year = –10 lg (T_closed / 365 * 10^{-Δ_closed/ 10}  + T_open / 365 * 10^{-Δ_open/ 10} )

In which

Δ_closed = insulation with windows closed

Δ_open = insulation with windows open

T_closed = number of nights with windows open

T_open = number of nights with windows open

Default values for insulation for windows closed depend very much on building practices (single, double or even triple glazing). Open windows usually give attenuation from 5–10 dB, slight open windows 10–15 dB. Surveys indicate that windows may be kept open (or half‑open) for more than half of the time, even in colder climates (75 % in the Netherlands)."

Noise abatement course 2010 ("ME1", UEF)

From lecture "Sound insulation" (doc. E. Björk):

Sound insulation of facade

condition	delta LA
ventilation window open	< 10 dB
ventilation window slightly open	< 15 dB
2-glazed window	25-35 dB
3-glazed window	30-40 dB
window + balcony glazing	40-45 dB

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Outside-inside difference in environmental noise levels. Opasnet . [1]. Accessed 20 Dec 2024.