and the impact of sound insulation, social norms and other factors
INTRODUCTION
As part of the policy of deregulation introduced by the government of the Netherlands, the Ministry of Housing, Spatial Planning and the Environment has scrutinized regulation and policy on "noise from neighbours". There have been studies into this area in the past (1, 2, 3, 4, 5), which show that both the scale and severity of noise annoyance from neighbours is substantial, and by order of size equates to the annoyance from traffic noise. Sounds from neighbouring dwellings can be heard in approximately 75% of dwellings in the Netherlands, and in 40% of cases this is a daily event. In approximately 1/3 (= 2.2 million) of all households at least some level of annoyance is experienced from these sounds; in approximately 13% (= 850,000 households) to a severe degree. It is also found that the noise annoyance problem is highly complex. In summary, the following factors are at play:
a) sounds are produced and these are connected with occupant behaviour which is necessary and/or desired, and with norms which the "transmitter" of these sounds applies;
b) there is some degree of sound insulation between dwellings. This in conjunction with a) is what determines the "dose" i.e. the sound(level) that penetrates the "recipients" dwelling;
c) There is a collection of highly diverging auditory and annoyance experiences in the dwelling of the recipient: the effect. These experiences are connected with such factors as the degree of disruption that occurs and norms applied by the "recipient" himself and what he expects from others (the neighbours). Furthermore, both "transmitters" and "recipients" may vary markedly at an individual level and from person to person (in terms of lifestyle, behaviour, attitude and/or by situation).
Given the above complexity and the scale and degree of annoyance experienced in the Netherlands from noise from neighbours, further investigation was deemed necessary, particularly into:
- the dose-effect relationships, i.e. the relationships between sound insulation and dwellings on the one hand and the ability to hear sounds from neighbours and the annoyance caused on the other;
- the "social norms" applied by the transmitters and recipients of noises from neighbours.
The results of these studies, and the results of an analysis of the effectiveness and applicability of instruments to achieve the objectives of policy (reducing noise annoyance in the residential environment, notably serious annoyance) will be or have been incorporated into a policy memorandum entitled "Noise and housing" which has been published by Ministry of Housing, Spatial Planning and the Environment (6).
The study into social norms deals with the question of which norms occupants apply to themselves and their neighbours, what tolerance they display in relation to certain types of noise (sources) in terms of duration, frequency, volume and times, and what noise-abating facilities, behavioural changes or other solutions to specific forms of neighbour noise that the occupants feel could effectively be used to reduce noise and/or annoyance. This study was carried out by RIGO Research en Advies BV in 1242 households (7).
The TNO dose-effect investigation showed that the scale and severity of noise annoyance from neighbouring dwellings corresponded well with the national data quoted on the subject and with the results of the RIGO study. 10% had had serious annoyance from these sounds and 32% to some degree (in the RIGO study the figures were 14% and 31% respectively). Almost half of the respondents (47%) said they could hear daily noise from neighbouring dwellings. Table 1 shows the results of the TNO study when it comes to hearing (at least monthly) and the annoyance caused by specific noises. Flushing sounds from the neighbours toilets are the noises most commonly heard. The risk of annoyance is largest if what in principle are avoidable "noisy" sounds are heard: special pop music, having the TV/radio/audio equipment on loud, slamming doors, walking heavily on the stairs or on floors, DIY (do it yourself) noises or speaking with raised voices or shouting. There is least chance of noise from spin-driers, washing machine or "normal" unavoidable day-to-day noises: the shower and/or bath, "normal" talking and "normal" walking on floors or stairs.
In the ground floor dwellings in low-rise buildings in general more noise is experienced than in the other types of dwellings investigated, particularly caused by "normal" walking sounds. It is not possible to say whether this corresponds to the national situation on account of the limited scope of the study, but the results agree in with previous studies (9).
Table 1 Priority of hearing (if this occurs at least monthly) and degree of annoyance (if sounds are heard at least monthly) from specific noise sources from neighbouring dwellings.
| priority of
hearing |
priority of annoyance | Types of noises or noise source |
|
average annoyance with monthly hearing (scale 1-10) |
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Flushing sounds from toilet |
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DIY sounds |
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Noise from TV/radio/audio turned up loud |
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Slamming of doors |
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Speaking with raised voices or shouting |
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Walking heavily on stairs |
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Dog barking |
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'Normal" walking on staircase |
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Noise from walking heavily on floors |
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walking heavily on floors |
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Sounds from spindrier or washing machine |
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Noise of showering and/or taking bath |
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Playing special popmusic |
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Speaking normally |
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Noise from TV/radio/audio at normal volume |
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It was found in establishing dose-effect relationships that the dose-units used at individual (personal) level can not predict or have little predictive value of the noise annoyance experienced from neighbouring dwellings. In itself this is not so surprising, as for each individual a range of individual- and dwelling-related factors play some part in experiencing annoyance from certain sounds. At an individual level, only weak but still significant (p < 0.05) linear dose-effect relationships were found between Ilu (an index of airborne sound) and general annoyance (with an "explained" variance of 7%) and also between Ilu;k and sound from flushing the toilet, and between the calculated sound insulation category (GWK) and noise caused by "normal" talking by the neighbours.
If the individual respondents, however, are grouped in dosage categories, it is found that the percentage experiencing annoyance and/or the degree of annoyance experienced in many cases clearly diminishes in proportion to the quality of the sound insulation. This particularly applies to severe annoyance. For example this is the case with the relationship between general annoyance and Ilu (see figure 1), and annoyance caused by TV/radio/audio equipment being on loud, people walking heavily on floors and by showering and taking baths in neighbouring dwellings in relation to the calculated GWK (see figure 2).
Figure 1 Percentage seriously affected (A72), affected (A50) and affected to some degree (A28) as a function of airborne sound insulation ( in llu )
Figure 2 Average annoyance caused by specific noises in neighbouring dwellings as a function of the sound insulation category (GWK)
The dose-effect relationship for airborne sounds identified in the study corresponds reasonably well with the results of a previous study (3). Admittedly, the dose-effect regression line is less steep than the line in the previous study. With an Ilu of 0 dB, there are approximately 10% fewer people severely affected and 35% to some extent affected, with an Ilu of +7 dB, approximately 5% severely affected and 25% to some degree affected. In the previous study, there were 10% severely affected and 25% to some degree affected at 0 dB and 2.5% and 10% affected at +7 dB respectively.
No clear link was found with regard to impact sounds: between Ico (an index of impact sound) and annoyance caused by impact sounds (walking, slamming doors, etc). Regardless of the Ico measured (ranging from -7 to +37 dB) there are approximately 10% severely affected and 35% to some degree affected. In the previous study (3), there were 25% severely affected and 50% to some degree affected at 0 dB, and 10% severely affected and 25% to some degree affected at +6 dB. A possible explanation of the lack of any link between the impact sound insulation and the annoyance is that Ico values of lower values than 0 dB were measured in too limited a number of dwellings (it was the actual situation that was measured i.e. including carpeting). A further reason may also be (more so than with airborne sounds) that impact sounds cause annoyance regardless of the level or type of source. More detailed studies, for example into the effect of carpeting and the positioning of the measuring point is felt to be necessary.
A large number of factors determine whether sounds from neighbouring dwellings which are heard actually cause annoyance. The following factors were found to be at play:
It was also found that the annoyance caused by noise from neighbouring dwellings was closely connected with the rating (in terms of excellent, good, (just) adequate, inadequate or poor) that one gave to the sound insulation of the dwelling in relation to neighbouring dwelling(s). A further factor was that annoyance was fairly closely connected precisely with "noisy" sounds: mainly special pop music, having the TV/radio/audio equipment on loud, slamming doors and walking heavily on floors. The study also showed that the relationship between the "subjective" judgement by residents of the quality of the sound insulation in relation to neighbouring dwelling on the one hand and the dose-units applied on the other is slightly stronger than that between the annoyance and the dose-units referred to above. In other words: the dose-units appear to give a better prediction of the quality rating of the insulation (the "noisiness" of the dwelling) than the annoyance.
The quality judgement of insulation appears to be mainly determined by the sounds of "normal" day-to-day behaviour from neighbours from such "normal" talking, taking showers or baths, the noise from a spin-drier or a washing machine, and "normal" walking on floors and stairs. The poorer the judgement of the insulation, the greater the annoyance experienced from the "normal" behaviour listed above. What is striking is that hearing the sound of a toilet flushing, slamming of doors and barking of dogs from the neighbours appears to have less impact on a good or excellent assessment of sound insulation than other sounds. In other words: it would appear that the sound of the toilet flushing, the slamming of doors, the barking of dogs, etc is not primarily associated with the level of sound insulation; as if one believes that these sounds couldnt be insulated against anyway.
If one looks in particular at the factors considered which are most closely connected with noise annoyance from neighbouring dwellings, it is found that the greatest reduction in noise annoyance occurs if :
- the judgement of the quality of the sound insulation to the neighbours is improved;
- less annoyance is experienced from "normal" talking at the neighbours;
- satisfaction with the dwelling (particularly its technical state of repair) is improved.
An increase in annoyance from noise from neighbouring dwellings can be expected if:
- sound insulation in relation to the exterior is improved, but not in relation to adjacent dwellings.
Finally, there are a number of factors that can be listed which did not display any significant link with annoyance in the present study. These include whether they were dwellings for rental or purchase (according to the inhabitants), the front exterior is thermally and/or acoustically insulated. Nor was any link established with personal characteristics such as sex of respondent, having been born in the Netherlands or not, being hard of hearing or not, level of education and (according to respondents own statements) being part of a busy or calm household.
Almost all respondents (approximately 95%) in the TNO study said they took the neighbours into account with their own behaviour. Most of them (3/4 of respondents) did so when setting the volume on their TV/radio/audio equipment. Approximately 15% of respondents attempted to avoid stamping on floors or slamming doors.
80% of respondents considered they were very tolerant with regard to noise from neighbours and only 3% regarded themselves as not being tolerant at all. If tolerance is defined as "sensitivity to annoyance from noises", or the risk of annoyance when hearing sounds, this particularly applies, as indicated above, to avoidable "noisy" sounds such as loud pop music or people walking noisily on floors. People were most tolerant of the sounds of toilets flushing, the sounds of showers and/or baths, "normal" walking sounds on floors and staircases and "normal" talking at the neighbours. As against that, it was also found that if "normal" talking and TV/radio/audio equipment at "normal" levels at the neighbours is heard, the annoyance tends to increase, in proportion to the quality of the airborne sound insulation. No "off the shelf" explanation can be found. In the study into social norms conducted by RIGO, it is assumed that residents in reasonably to well insulated dwellings are less inclined to be cautious about their own noise production. It is also conceivable that people who live in poorly insulated dwellings are more tolerant than in well-insulated dwellings. This point did not clearly emerge from the TNO study.
The RIGO study paid particular attention to the norms that people apply to noise-generating residential behaviour. The study covered the times, locations in the house, duration, loudness and frequency at which noises from neighbours are allowed to be audible in the house. In particular, this means sounds from sanitary fittings and installations, radio, TV and stereo sounds, impact sounds, DIY sounds and pets. Approximately two thirds of the people apply specific norms in terms of timing, duration of frequency or at least one source. Others consider it normal to always hear noise from the neighbours often or consider it unacceptable to ever hear a sound from the neighbours. The study identified how many people endorse particular norms for specific sounds. This enables some understanding to be gained of what constitutes "normal" situations for the majority of a population. On this basis, one can in principle establish which "general" norms should have to be applied for only a limited number of people to experience annoyance from audible sounds from neighbours. Where these norms are set, depends upon the (policy) question of how many people find it acceptable to be troubled by noise from neighbours. Table 2, as an arbitrary example, indicates what conditions are required for various types of sounds that are just audible not to be experienced as annoyance in no more than 20% of households on weekdays (on Sunday the starting time is one hour later) (see table 2):
Table 2 Conditions for maximum of 20% annoyed by hearing different types of noises
| Time (weekdays) | Duration | Frequency | |
| sanitary fittings and installations sounds | between 7.30 - 22.00 hours | < 5 minutes | several times a day |
| impact sounds | between 8.00 - 20.00 hours | < 10 minutes | several times a day |
| radio, TV and stereo | between 9.30 - 20.00 hours | < 8 minutes | 6 times a year |
| DIY sounds | between 8.00 - 20.00 hours | < 10 minutes | 6 times a year |
| Pets | between 9.00 - 18.00 hours | < 10 minutes | maximum once a year |
Noise from neighbours which is so loud that one has to modify ones own behaviour (speak more loudly, turn up TV) is virtually never found to be acceptable. The only exception to this is noise which is announced in advance, e.g. parties or DIY activities.
What people consider "normal" depends upon their personal or household situation, but also, for example, the quality of the dwelling, relationship with the neighbours, whether one hears noise from the neighbours oneself and the specific noise that one hears from the neighbours. There are no indications that norms for ones own noise-producing behaviour differ markedly from the norms applied to the neighbours. If one lives next to neighbours with different norms, the risk of annoyance increases, most (in ascending order) if the norms differ about the time of noise production ending, duration, frequency and loudness. The more the neighbours can be held responsible, the greater the annoyance experienced.
The RIGO study examined what residents themselves consider the most effective means of countering noise from neighbours. It was found that less than half of the Dutch (affected by noise) took action against noise from neighbours and if action was taken, it was effective in a third of cases. According to residents, going to talk with the neighbours is the most effective means. Knocking on the wall or informing the tenant are used significantly less, but can prove effective, although in many cases this will be at the expense of the relationship with the neighbours. The latter point certainly applies if the police are called in. The annoyance is then more likely to increase than decrease, as it is likely, so it is assumed, that people will be less inclined to impose restrictions upon themselves to avoid noise from the neighbours if relationships are poor and because other ways of doing something about the annoyance are then ruled out. It is found that physical measures, such as better insulation of the dwellings or using door-closers for example, are hardly mentioned and are used extremely sparingly.
CONCLUSION
The main conclusion that can be drawn on the basis of the TNO and RIGO studies described above are as follows:
- Annoyance caused by noise from neighbouring dwellings and from the noise of neighbours outdoor activities is a comprehensive and complex problem. This is again confirmed by the present study.
- It was found in establishing the dose-effect relationships that the "heaviness" of the insulation (the dose) has little or no predictive value of the noise annoyance from neighbouring dwellings at individual (personal) level. If individual respondents, however, are grouped by dose (or insulation) categories, it is found that the percentage affected clearly falls in many cases in proportion to the measure of the sound insulation. This particularly applies to those severely affected by the annoyance.
- Major factors that affect noise annoyance from neighbouring dwellings include hearing specific (notably noisy) sounds from the neighbours, satisfaction with ones dwelling in general (notably its technical state of repair) and the individuals opinion of the quality of the insulation of the dwelling (or the 'noisiness'of the dwelling).
- The (physical) units in which insulation quality is expressed is more closely connected with the judgement of insulation quality than with the annoyance experienced. In other words: improving the judgement of the sound insulation is connected with achieving better (measurable) insulation values. Indirectly, although less clearly, this also affects the annoyance.
- Some of the sounds that cause annoyance such as talking at "normal" volume, taking a shower or bath and using the toilet, are a result of activities in which everyone engages and which are unavoidable or virtually so. If these sounds can be heard (which is the case in a significant number of dwellings), the "subjective" judgement by residents of the quality of the sound insulation of the dwelling is more negative. This judgement, and thus indirectly the annoyance, can in principle be improved by fitting better insulation. If the respondents are grouped in dose-categories, it is found that annoyance in general and annoyance caused by a number of specific sounds clearly diminishes in proportion to the airborne sound insulation.
- Behaviour which in principle is avoidable such as having a TV/radio/audio on loud, slamming doors, walking heavily on floors and staircases, shouting, drilling and the barking of dogs correlate less strongly with the judgement of the quality of sound insulation in the dwelling. Serious annoyance caused by such factors often can not be avoided by better sound insulation. By far the majority of respondents (95%) claimed that they took account of the neighbours in their own behaviour and a large number of them (80%) considered themselves tolerant of noise from neighbours. This means that the scope for reducing noise annoyance which in principle is avoidable by behavioural changes and raising tolerance levels is limited. In many cases, the annoyance will be caused by noises which could be avoided at certain times, but which are difficult to avoid at all times.
- The study gained some understanding of what the population generally considers still acceptable when it comes to times, duration, frequency and volume of various types of sounds. This enables "general" norms to be set and (policy) decisions to be made on what percentage of (severely) affected is the maximum permissible or feasible. These norms can form the reference framework for residents affected and those causing annoyance, intermediary bodies and enforcers (police e.g.)
- If good sound insulation is in place, people expect to hear less, which means that annoyance may be perceived at lower sound levels. This indicates that it is unlikely that one could ever reduce the noise annoyance from neighbours without behavioural changes. Nevertheless, one can expect that apart from focusing on better 'low-noise design' and care during the construction phase, relatively simple physical measures could be applied more to reduce specific forms of annoyance, notably that caused by "normal" day-to-day sounds. This means that less noise will be produced without having to modify ones behavioural norms. If such measures are to be used more, greater publicity will have to be given to it, given their sparing application at present.
- One can expect noise annoyance from "noisy" sounds which cannot always be avoided (such as noisy music from young people in their bedroom, music with windows open during a party with other people, the occasional slamming of doors or walking heavily, elderly people who are hard of hearing having the TV on loud, drilling when doing jobs around the home, etc.) will increase the closer people live together. With "compact building", extra attention will therefore be required to bring about adequate sound insulation against normal sounds, but a greater risk of annoyance connected with a larger number of people in their immediate environment is inherent to compact building.
Literature
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