PROCEEDINGS of the23rd International Congress on Acoustics
9 to 13 September 2019 in Aachen, Germany

Perception of combined indoor noise sources in lightweightbuildings
Alessia FRESCURA; Pyoung Jik LEE;
Acoustics Research Unit, School of Architecture, University of Liverpool, Liverpool, UK

ABSTRACTContrary to community noise field, the combined effect of multiple noise sources on annoyance havenot been investigated in building acoustics. Therefore, the present study aims to quantify the totalannoyance and emotional reaction caused by indoor noises from the upstairs and next-door neighbours.
Footstep sounds were recorded in a laboratory equipped with a timber joists floor in different
configurations. Listening tests were then performed to assess the relationship between psychologicalvariables (annoyance, arousal, and valence), physiological measurements (fEMG, EDA, heart rate andrespiration rate) and sound stimuli in several scenarios. In the first part, the perception of individual
impact and airborne noise was evaluated considering the sound insulation performances of different walland floor structures. The participants were also asked to evaluate the total annoyance, arousal andvalence in the second part when impact and airborne sound sources were presented at the same time.
Annoyance ratings for both single and combined noise sources were mainly affected by the soundpressure level; however, sharpness also contributed to the annoyance ratings. It was also observed thatthe annoyance ratings of the combined noise sources were influenced by the sound insulation
performances of the wall and floor. The findings of this study would be helpful to understand how weperceive the combination of noise sources we are usually exposed in timber houses.

Keywords: Lightweight buildings, Annoyance, Combined noise sources

1. INTRODUCTION
Interest in lightweight constructions is flourishing in Europe. Timber buildings, in particular, offer amore environmentally sustainable alternative compared to traditional heavyweight constructions.
However, acoustics comfort in such spaces is still not sustainable for dwellers. For instance, in multistorey lightweight residential buildings, residents are frequently exposed to impact noise caused byupstairs neighbours as well as airborne noise transmitted from side units. This noise exposure negatively
impacts the occupants causing stress and reducing the quality of psychological well-being in their home.
Annoyance due to combination of noise sources has been previously investigated in community noisefield. As a result, different models have been proposed and tested in order to predict the total annoyancecaused by environmental noise sources such as aircraft, road traffic and railway noise (1, 2). The
combination of acoustic sources has also been studied to enhance urban soundscape. Particularly, adding
water sounds to urban sound field resulted to be effective by masking urban noise such as construction
sites and road traffic (3). Previous study also highlighted the key role of non-acoustic factors in theevaluation of the total annoyance caused by combination of noise sources (4). Moreover, noise
sensitivity was an essential variable in understanding subjective responses to environmental andbuildings noise, specially floor impact noise in apartment buildings (5). In order to assess noise

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sensitivity, NoiSeQ questionnaire was developed to identify noise resistant and noise sensitiveindividuals (6).
The perception of acoustic stimuli is influenced by its emotional experience. In particular, acoustic
stimuli might evoke sensations and emotional reactions which may also imply or affect quality
judgments (7). The perceived emotions can be recorded in the orthogonal dimensions of arousal andvalence using Self-Assessment-Manikin Scale (SAM). A number of studies used this approach toevaluate reactions to acoustic stimuli (8, 9) shifting the focus toward listeners and contextual
characteristics instead of physical characteristics of the signal.
The goal of the present study is to investigate the psycho-physiological responses to single andcombined noise sources. It was hypothesized that psycho-physiological responses to noise might bedifferent across types and combinations of noise sources. Floor impact noise transmitted from theupstairs neighbours was used as a major type of noise stimuli and airborne noise source from the sideunits was added to the floor impact noise. Laboratory experiments were conducted with 20 participants.
Noise annoyance, arousal and valence were evaluated after each stimulus presentation, and fourphysiological measures (fEMG, EDA, heart rate and respiration rate) were monitored throughout theexperiment.

2. METHODOLOGY
2.1 Participants
Twenty adults (8 males and 12 females) with self-reported normal hearing took part in the experimentso far. The participants aged between 22 and 33 (mean= 27.8 and std= 2.7) and their nationality varies
across eight different countries. Seven of them reported to be commonly annoyed by neighbour noises
in their actual house. The self-reported noise sensitivity measured using NoiSeQ ranged from 28 up to70.
2.2 Noise stimuli
Five different noise sources were selected as representative of typical impact and airborne noises
heard in residential buildings. Three of them are floor impact sources consisting of different footsteps:
an adult walking at different paces (normal, 108 bpm and fast, 132 bpm) and a kid running. Others areairborne sources from neighbours: speech (conversation between two people) and piano music. Floor
impact noises were recorded in the acoustics laboratory at Rosenheim University of Applied Science,
where a lightweight timber joists floor is separating the vertically adjacent source and receiving rooms.
The floor area of the receiving room was 21 m2 and its volume was 53 m3. Sound absorbing panels wereinstalled in the receiving room so measured reverberation time of the receiving room was around 0.5 s.
Sound recordings were carried out with four different configurations: 1) bare timber joists withchipboard on top; 2) bare timber joists and chipboard with sand floating floor installed; 3) bare timber
joists and chipboard with suspended ceiling, and 4) bare timber joists with chipboard with suspended
ceiling and floating floor. For each configuration, 5mm thick carpet on the floor was used as a floor
finish and additional recording was also performed without floor covering. A female adult with a weightof 50 kg and a height of 1.65 m and a five years old child with a weight of 22 kg were chosen as generalwalkers. A-weighted maximum sound pressure levels (LAFmax) were measured using a microphone(GRAS, 40HL) when adult and kid walked or ran diagonally in the source room. The LAFmax of the adultwalking ranged between 27 dB and 56 dB, while the kid running showed a smaller range from 33 dB to51 dB. As listed in Table 1, the ranges of noise stimuli in the present study correspond to the range ofthe recordings. Thus, the adult walking varied between 30 and 55 dB as an interval of 5 dB, while, thelevel of the kid running changed from 35 to 50 dB. The sound recordings representing each level werechosen as noise stimuli. For example, 50 dB of the adult walking (normal pace) was recorded from thebare timber joists with chipboard on top and carpet. The airborne noise sources were anechoicrecordings. The spectral characteristics of the airborne noise sources were modified to simulate threelightweight partitions with good, medium and poor sound insulation performances (Rw=52, 43, and 33
dB respectively). It was assumed that A-weighted equivalent sound pressure level (LAeq) of the speech
and music 79 and 80 dB in the neighbour’s houses (10); thus, the ranges of the filtered sound stimuli
were slightly different. Frequency characteristics of the noise stimuli are plotted in Figure 1. Most noise
stimuli had dominant sound energies at low frequencies below 100 Hz. However, several sounds also
showed strong sound energies at high frequencies. Those were recorded on floor structures with a25141

configuration not effective in reducing the transmission of noise in the high frequency range, such aswith no floating floor or carpet.
Table 1 – Sound pressure levels of noise stimuli; LAFmax for impact sources and LAeq for airborne sources
SourceImpactAirborne

Levels [dB]
Adult walking at normal speed

30 – 35 – 40 – 45 – 50 – 55

Adult walking at fast speed

30 – 35 – 40 – 45 – 50 – 55

Kid running

35 – 40 – 45 – 50Speech

24 – 29 – 42Music

25 – 29 – 44

Frequency [Hz]5142

Frequency [Hz]3

Figure 1 - Frequency characteristics of noise stimuli.
2.3 Experimental design
The experiment took place in an audiometric booth with low background noise level. Participants
were sitting on a comfy chair and asked to answer questionnaire through VBA designed interface
presented on a monitor. The stimuli were presented diotically through headphones (DT 770 Pro) and asubwoofer (SONAB System 9 CSW-71000) which was placed in front of the participants. Sounds above
63 Hz were presented via the headphones, while low-frequency sounds below 63 Hz were presented via
the subwoofer. White noise (NC 25) was presented through headphones throughout the experiment as
an ambient noise in the living room.
The experiment was composed of four sessions (three combined noise sessions and one single noisesession). There were breaks between sessions to avoid excessive fatigue and loss of concentration. In
the single noise session, each of the impact and airborne noise sources were presented for 15 minutes,
while in the remaining sessions, the impact noise combined with airborne noise sources were presented
for 21 minutes each. All noise sources and sessions were randomized across participants to avoid ordereffects. Each session consisted of the repetition of the following 40s sequence: 10s of baseline with apresentation of black screen; 20s of sound stimulus (single or combined noise sources) together with apicture of a living room on the screen; the final 10s for answering questions on the screen. Before thestarting of the experiment participants were asked to answer the 35-items questionnaire NoiSeQ in order
to assess their noise sensitivity. A training session was also designed as familiarizing phase with thenoise stimuli and questionnaire form. During the experiments, participants were asked to imagine being
relaxing in their own home. The study was ethically approved by the School of the Arts Committee on
Research Ethics, University of Liverpool.
2.4 Assessments of psycho-physiological responses
After listening to each stimulus, the participants were asked to rate their annoyance on an 11-point
scale (0 = ‘Not at all’ and 10 = ‘Extremely’). Furthermore, two Self-Assessment Manikin (SAM) 9pointpictorial scales were used to assess arousal and valence. In the present study, four physiological measures
were investigated: 1) facial electromyography (fEMG), 2) electro dermal activity (EDA), 3) hart rate(HR) and 4) respiration rate (RR). All the physiological responses were recorded on a computer using a
MP 150 WSW digital acquisition system (BIOPAC systems) and were analysed using AcqKnowledge
4.4 Software (BIOPAC systems).

3. RESULTS AND DISCUSSION
3.1 Psychological responses: annoyance
Figure 2 shows mean annoyance ratings for the single floor impact noises and the combinations offloor impact noise and speech noise (airborne). Specifically, thick black lines indicate the annoyance
ratings of the single noises, while grey lines represent those of the combined noise sources. It was

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observed that the annoyance ratings increased as the increase of sound pressure level for three different
impact sources (adults walking at normal and fast speed, a kid running). However, for the adults walking
noises, the participants rated the stimuli at 45 dB less annoying than the stimuli at 40 dB. This is mainlybecause the stimuli at 40 dB had much stronger sound energies at high frequencies compared to otherstimuli. It was also found that different sound insulation performances of the wall partitions significantly
affected the annoyance ratings. For the highest sound insulation performance (Rw=52), the annoyance
ratings of the combined noise sources were quite similar to those of the single noise sources without
airborne noise source. On the other hand, other combined noise sources from the wall with Rw=43 and33 showed significantly higher annoyance ratings than the single noise sources. More specifically, theinfluence of the addition of airborne noise sources to the floor impact noises was different across thesound pressure levels of the floor impact noises. The annoyance ratings of the floor impact noises ranged
between 30 and 45 dB were remarkably increased with the addition of the airborne noise sources with
Rw=43 and 33. The effect of the adding airborne noises on the annoyance ratings became less above 45
dB of the footsteps noise. For instance, for the impact sources at 55 dB, the annoyance ratings werealready greater than 9 on an 11-point scale.

Figure 2 - Annoyance ratings for single and combined noise sources
3.2 Analysis of sound quality metrics
As shown in Figure 2, the annoyance ratings of the stimuli at 45 dB were lower than those of thestimuli at 40 dB for both normal and fast paces. This indicates that the sound pressure level is not
sufficient to fully explain the annoyance ratings. Therefore, sound quality (SQ) metrics were introduced
to understand the relationships between SQ metrics and annoyance ratings. Loudness, sharpness,roughness and fluctuation strength were calculated using BK Connect (Brüel & Kjær). Loudness wascalculated according to ISO 532-1, which describes the procedures for calculating the time-varying
Loudness. During the calculation of roughness, sharpness, and fluctuation strength, the time interval
between the spectra was set at 2ms.
Multiple regression analysis was then conducted using a linear combination of SQ metrics to calculate
the effects of SQ metrics on annoyance. It was found that the best combination of variables with respect
to the correlation between the annoyance and SQ metrics was loudness and sharpness. The standardized
partial regression coefficients of variables ܽଵ and ܽଶ in equation (1) were 0.64 and 0.38 respectively,
and these coefficients were statistically significant (p < 0.05 for ܽଵ and ܽଶ ). Using these values, theobtained total coefficient (0.91) was significant (p<0.05). Coefficients ܽଵ and ܽଶ had positive values,
therefore greater loudness and larger sharpness result in higher annoyance. As plotted in Figure 3, theannoyance ratings predicted by using equation 1 showed good agreements with the measured annoyanceratings.
‫ ݁ܿ݊ܽݕ݋݊݊ܣ‬ൎ  ܽଵ ݈‫ ݏݏ݁݊݀ݑ݋‬൅  ܽଶ ‫ݏݏ݁݊݌ݎ݄ܽݏ‬5144(Eq 1)

5108642

Fast speed
Normal speed

00246810Annoyance predicted

Figure 3 - Relationship between measured and predicted annoyance ratings for adults walking at normal
and fast paces.

4. CONCLUSIONSThe present study measured the participants’ subjective responses (annoyance, arousal and valence)and physiological responses (fEMG, EDA, heart rate and respiration rate) to single and combined noise
sources commonly heard in lightweight residential dwellings. It was found that the annoyance ratings ofthe single noise sources were different from those of the floor impact noises combined with an airborne
source (i.e. speech). The annoyance ratings of the combined noise sources were influenced by the soundinsulation performances of the wall and floor. Analysis of the sound quality metrics also showed thatthe annoyance ratings were dependent not only on loudness but also sharpness related to the frequency
characteristics of the noise stimuli. The laboratory experiment is still on-going and additional 20
participants will take part in this study. The results of the emotional dimensions (i.e. arousal and valence)
will be presented together with the ongoing analysis of the physiological measurements at theconference.

ACKNOWLEDGEMENTS
This project has received funding from the European Union's Horizon 2020 research and innovation
programme under grant agreement No 721536.

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