Apphed Acoustws 27 (1989) 147-152

Technical Note

Reduction of Noise Nuisance from Footsteps on Stairs

A BS TRA C T

Soctal surveys conducted by the Budding Research Estabhshment ( BRE) have tdentzfied tmpact norse from netghbour's footsteps on statrs as one of several spectfic norse problems experwnced by the occupants of modern dwelhngs Laboratory and field measurements have been made to evaluate the reductton m nozse level that can be achwved by laying vartous types of resthent matertal over the stair treads For ttmber stairs the effects of tsolatmg the statrcase from the budding structure and relocating the statrcase wzthm the dwelhng were also evaluated Useful reductlons m tmpact notse were achwved The effect of other destgn features such as party wall type, were also exammed and the effects were found to be smaller

INTRODUCTION

BRE surveys 1,2 have shown that many people who hve m attached dwelhngs are disturbed by impact noises such as footsteps on stairs and banging doors, caused by nelghbours in other parts of the building This paper descnbes laboratory and field studies of ways of reducmg noise from footsteps on stairs Work on the reduction of noise from banged doors has already been reported? For timber stairs, the effects on impact no~se transm~ssmn of isolating the staircase from the building structure and reposiUonlng the staircase within the dwelhng were examined The effect on impact noise transmission of other design features such as party wall mass and type, e g sohd or cavity, were examined for both timber and concrete stairs but the effects were found to be smaller.

147 © 1989 Crown Copyright

148 J E Savage, L C Fothergdl

TEST FACILITIES A N D E Q U I P M E N T

The laboratory tests on stairs were conducted in an existing building at BRE This building was brick bruit with four rooms, each of volume 40m a, at ground and first floor levels All internal wall surfaces had a plaster finish Double acoustic doors and secondary windows were fitted to increase insulation against external noise

For the measurements a standard timber staircase was fitted next to the 225-mm thick brick party wall m a way representative of site practice, i e fixed at the top and base together with six equally spaced screws at the side Subsequently the six screws were removed and the staircase was supported on rubber pads to isolate it from the building structure

Measurements were also conducted in newly completed dwelhngs just prior to their occupation Measurements were made in pairs of buildings which differed In the detail under investigation but were as similar as possible in other respects The project period coincided with one of low budding activity and consequently not all common building construction types were available for measurement The reslhent materials that had performed best m the laboratory tests were tried on both timber and concrete stairs when fixed to walls of different mass and type, I e solid or cavity

M E A S U R E M E N T M E T H O D

All laboratory and field measurements were made using an ISO tapping machine as the noise source It was positioned in turn on four different stair treads, and the resulting noise levels in the 1/3 octave bands from 100 Hz to 3150Hz were measured in the adjacent room using six microphone positions

R E S U L T S A N D D I S C U S S I O N

The structure-borne component of the noise can be reduced by isolating the staircase from the structure and both airborne and structure-borne components can be reduced by a soft covenng In the laboratory the effect o f isolating a timber staircase from a sohd brick wall compared with the effect of a soft covering is shown m Fig 1. Isolation resulted m a substantial reduction m noise level, particularly at low frequencies, which is important as footsteps produce mainly low frequency noise This reduction m noise due to Isolation can be compared with the effect of vinyl floor covering laid over

Reductton o f norse nutsance f rom footsteps on stairs 149

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Fig. 1. Noise level m recewmg room with (a) stairs fixed to party wall, LnT w : 56, (b) stairs Isolated from structure, LnT w = 49, (C) stmrs fixed to party wall but with a soft covenng of

foam backed wnyl, L.T w = 44

foam underlay on the treads of the same staircase with the stairs screwed to the wall The reduction due to the soft covering is less at low frequencies but much greater at high frequencies However, there is some evidence that a soft covering reduces noise from the ISO tapping machine by a greater amount than from footsteps 4 Consequently the reducUon in noise due to the soft covering may not be as good subjectively as the measured results suggest Isolating the staircase from the structure IS probably only practicable in very noise sensitive environments but it does have the additional advantage that regular replacement of a soft covenng is not necessary.

The worst position for the stairs is against the party wall with a noise sensmve room on the other side F~eld measurements show that mount ing the stairs on an Internal masonry wall abutting the party wall offered little reduction in noise transmission The stairs had to be located at the far side of the house to achieve an appreciable reduction m Impact noise, of say 10 dB, as shown in Fig 2 With a timber staircase adjacent to a masonry party wall, field measurements showed the party wall had an effect on transmission of

150 J E Savage, L C Fothergdl

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C o m p a r i s o n o f the noise level m the adjacent house w h e n the t imber staircase Is

mounted (a) against the party wall, LnT ,, = 56, (b) at the far end of the house, LnT w --"- 44

impact sounds Heavy masonry walls, either solid or cavity, having a surface mass m the region of 400 kg/m 2 transmitted less impact sound than walls o f hghter concrete Where hghtwelght concrete had been used, cavity walls had a shght advantage, although there was little difference at low frequencies

The type of staircase had a major effect on impact noise transmission The tapping machine on a concrete staircase produced less low frequency no~se than when on a timber staircase The timber staircase produced less noise at higher frequencies but this Is less important because soft coverings are effective at high f requenoes Typical field results are shown in Fig 3

C O N C L U S I O N S

At the design stage for new houses and flats the problem of impact noise transmission from footsteps on stairs can be mlnimlscd by locating staircases as far away from the party wall as is practicable Where staircase location cannot be effectively used it is advantageous to build the party wall

Reductton o f nmse nutsance from footsteps on ,tatrs 151

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Noise level in recewmg room with (a) timber stmrs without soft covenng, L.T ~ =

48, (b) concrete struts without soft covenng, L.r .w = 44

w]th high density materials Isolation of the sta]rcase from the structure is effective m mmimismg the problem but is probably not acceptable in dwellings, except in a very noise sensitive situation, because of movement of the stairs under foot and the complexity o f the design Concrete stairs perform better than timber stairs m that they produce less low frequency noise

Impact sound transmission can be significantly reduced by overlaying the stair treads with statable resilient materials Thls simple measure does not interact with other building dimensions and therefore is useful for both remedial work and upgrading In house conversion into flats

ACKNOWLEDGEM ENTS

The work described here was carried out as part of the research programme of the Building Research Establishment of the Department of the Environment and this paper is published by permission of the Director

152 J E Savage, L C Fothergdl

R E F E R E N C E S

1 Langdon, F J, Buller, I B & Scholes, W E, Noise from nelghbours and the sound insulation of party walls in houses J Sound Vzb, 79 (1981) 205-28

2 Langdon, F J, Buller, I B & Scholes, W E, Noise from nelghbours and the sound insulation ofparty floors and walls m flats J Sound Vtb, 88 (1983) 243-70

3 Savage, J E & Fothergdl, L C, ReducUon of noise nmsance from footsteps on stairs and slammed doors In Proc Inst Acou, Vol 8, Part 4 IOA, Edinburgh, 1986 pp 211-18

4 Carman, T A, Fothergdl, L C, Aubree, D, Josse, R & Vdlot, M A companson of methods for rating the insulation of floors against impact sounds Report to Budding Research Estabhshment, Garston, Watford and CSTB, Centre de Recherche de Grenoble, January 1988

J. E. Savage & L. C. Fothergill Budding Research Estabhshment, Garston, Watford WD2 7JR, UK

(Recewed 16 November 1988, accepted 20 December 1988)