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

Acoustically-friendly products - Sound quality as an emission
related product feature
André FIEBIG1
1

Technische Universität Berlin, Germany

ABSTRACT
People are permanently exposed to noise emitted by technical products in all areas of life. It is very muchknown that harmful noise effects are likely to occur by lower sound pressure levels as well. Moreover,residents complain about noises caused by neighbours according to the German Environment Agency with anupward trend. Moreover, acoustics is effectively one of the top product features regarding purchase decisions
and it seems that consumer journals increasingly ask for more information regarding acoustic comfort andsound quality. It is already well known that massive differences in the sound quality of products on themarket within the same product category exist. So far, some eco-labels have been established in the market
considering noise emission, but they often work with simple noise level indicators only. But, how to reliably
determine the sound quality of products representing sound perception and to widely spread this informationto consumer organizations and final consumers? The paper will present some case studies on product soundquality related metrics beyond sound power and will discuss options and difficulties to use sound quality
classifications for recognizing and supporting sustainable acoustically-friendly products.
Keywords: Sound quality, sound perception

1. INTRODUCTION
In everyday life, one is permanently exposed to all kind of noises. Most of the noises surrounding
us are emitted by technical products. Consequently, Schwela concluded that in all societies throughout
the world, the general population is increasingly exposed to environmental and consumer productnoise, however defined. The health effects of these exposures constitute an increasingly serious publichealth problem [1].
The amount of noise we are exposed to has a great impact on well-being and quality of life. For
example a survey has shown that in 2016 approximately 60 % of residents in Germany were annoyedby noises caused by neighbors [2]. Today, diverse studies have significantly proven that harmful noise
effects are likely to occur even by lower sound pressure levels [3].This is particular true when health isunderstood as “a state of complete physical, mental and social well-being and not merely the absenceof disease or infirmity” [4]. These statements underline the need to think about noise reduction andoptimization of technical products (such as all kind of vehicles, household appliances, HVAC systems,powered tools, etc.) on a large scale to reduce noise annoyance and adverse health effects.
Besides the aspect of noise related to health effects, noise is also considered to be a relevant productfeature influencing purchase decisions. According to American National Academy of Engineering,consumers rank noise as one of the top five product characteristics, when comparing productperformances (among characteristics like energy efficiency, price, reliability, maintainability) [5]. It
seems that different parties and stakeholders (consumer protection institutions, consumer journals,authorities, policy) increasingly demand more information regarding acoustic comfort and soundquality. In particular, in Europe over the past two decades product noise emission standards weredeveloped (e.g., voluntary limits that have been agreed upon by a nongovernmental body), regulations(e.g., noise measurements that must be complied with and certified), and efforts to increase the amountof information provided to consumers with respect to product noise emissions, such as voluntary andmandatory product labeling requirements [5].
For example, the EU energy label established already in 1992 as mandatory for household
appliances intends to indicate significant direct or indirect impact on energy consumption during use
1andre.fiebig@tu-berlin.de8003

[6]. The European Commission concluded that by improving the efficiency of energy-related products
through informed consumer choice benefits the EU economy overall [6]. Recently, the EuropeanCommission has adopted a format and visual identity of energy efficiency labels in order to makeenergy labels more understandable for consumers and help them make better informed purchasi ng
choices. These new labels will be visible for European consumers in physical stores and on-line by2021 [7]. According to the European Commission since its introduction twenty years ago, the successof the EU energy label has encouraged the development of ever more energy efficient products leading
to the problem of ceiling effect of the top class rated products asking for a rescaling (the majority ofproducts get an A++ or A+++). Noise statements in terms of A-weighted sound power levels aremandatory to be provided for most of the respective product groups. The European Commission
estimations value the total final accumulated energy savings of these new labels by 2030 to an amountequivalent to the annual electricity consumption of Hungary [7]. Thus, it can be concluded that less(noise) emissions will be beneficial for all involved parties, such as consumers, manufacturers, publiccommunities. However, it must be stated that eco-labels focusing on noise emission do only rarely
exists. In most cases, product noise as an indicator for unwanted, undesirable e mission during use is
not primarily addressed; in most cases noise is one aspect of a label dealing with all kind of emission
issues and energy consumption.

2. IDEA OF SOUND LABELS
A label is defined “as a written or printed matter accompanying an article to furnish identificationor other information” [8]. In the context of noise, a label might inform potential buyers and/or users
about the specific noise emission of a product. For it, different operating conditions must be
considered and probably combined to a sound label to be understood by buyers and/or users.
The information may be on a label affixed to the product or on the packaging, in a product brochureor user’s manual, or on a manufacturer’s website. If uniform labeling appears on all products, it can bea benefit to consumers, if it is not uniform, it can create confusion and be an unfair competitive
advantage or disadvantage [5].
However, William Lang complained that the noise information now available on most products isneither understood by the public nor widely available to them. He concluded that there is a global lackof understanding by manufacturers, suppliers, and potential users; and we noise control engineers are
partly responsible for this situation [9].
Moreover, it must be noted that there is no established and acknowledged label considering soundquality aspects so far. Almost all noise labels are focused on sound pressure/power level indicators.
Only rarely, other perception-related metrics and indicators are considered to classify the acoustic
comfort level. For example, product sounds can be relatively quiet but nevertheless they can berelatively annoying. The term ‘sound quality’ describes the perception of the suitability or desirabilityof a sound attached to a specific technical object emitting it. Efforts to develop an acoustic comfort
related label are rarely made so far.

3. EUROPEAN ECO-LABELS
So far, most of the noise-labeling programs are not mandatory but voluntary. In Europe anincreased public interest in information about products with reduced environmental impact wasobserved and the European Commission established the EU Ecolabel in 1992 [10]. This optional label
frequently called EU flower, which was introduced by a decree, has been developed to be a reference
for consumers with a focus on economic and sustainable products and services in order to reduce
environmental pollution. The EU Ecolabel can be requested by manufacturers, importers, traders (etc.)
at the national committee and is completely voluntary.
On a national level in Europe several eco-label programs were established over the last decades.
For example, the Blue Angel (Germany), the Nordic White Swan (Scandinavia), the Milieukeur(Netherlands), the TCO (Sweden) are valuing low (noise) emission products. Products with eco-labels
applying noise criteria include personal computers, printers, copiers, projectors, chain saws, garden
tools, and construction machinery. The Blue Angel indicates products, which clearly damage „ theenvironment less “ than comparable products of the same product group. The Blue-Angel awards thebest in class products. The Blue Angel eco-label has been well established in the market and considers
several emission criteria like noise in terms of the sound power level . The Blue-Angel eco-label isparticularly preferred in public tendering procedures [11].

80044. CASE STUDY – NOISE OF KETTLESAs a case study, kettles (water boilers) from 14 different manufacturers were measured, analyzed
and judged with respect to sound quality assessments.
The acoustic analysis of the kettle noises revealed large sound pressure level differences between
the different kettle noises (see fig.1). For example, differences of the A-weighted equivalentcontinuous sound pressure level LAeq were up to 10.5 dB ranging from 58.5 dB(A) to 69 dB(A). The
psychoacoustic loudness according to the ISO 532-1 [12] varied almost in factor 2 between thequietest and the loudest kettle, which means that the louder product was perceived as twice as loud as
the quiet kettle product (see fig. 2).

Figure 1 – Spectra of the noises from kettles boiling water. FFT vs. time (only left channel shown)

Figure 2 – Loudness of the noises from kettles boiling water. Loudness according to ISO 532-1 vs. time (leftand right channel shown)
Moreover, the psychoacoustic sharpness, determined by means of the German standard DIN 45692
varied over 25% as can be seen in figure 3. These sharpness values are only related to the timbre,
because the DIN 45692 does not apply an overall loudness dependency for the computation ofsharpness. According to the standard, an increase of sharpness is usually associated with an increase in8005

annoyance [13]. The analysis specific prominence ratio illustrates some “tonal” patterns [14]. The
different product noises exhibit different tonal magnitudes also varying in the respective frequency
region.

Figure 3 – Sharpness of the noises from kettles boiling water. Sharpness according to DIN 45692 vs. time(left and right channel shown)

Figure 4 – Specific prominence ratio analysis of the noises from kettles boiling water. Spec. prominence ratio
vs. time (only left channel shown)
Fourteen participants (9 male and 5 female) took part in the experiment and listened to kettle
product sounds, which were binaurally measured with a calibrated head measurement system (HMSIV) under controlled conditions. The sounds were presented via a programmable equalizer (PEQ V)
and headphones (HD 650) in a quiet listening room. The complete playback chain was calibrated andequalized.
In order to provide an associative context and to illustrate the design and size of the kettles, few
sounds were played back first and at the same time pictures of the different products were shown. After
this instruction providing a context for assessing kettle sounds, a short ‘training session’ took place,where participants familiarized with the evaluation tasks and provide first ratings, which were notconsidered for later analysis. In order to avoid sequence effects the anonymized sounds were played8006

back randomly. In agreement with ethical procedures, written consent was obtained from all of theparticipants.
In the first part of the experiment, the product sounds were judged by means of an 11-point
unipolar category scale with respect to ‘sound quality’. The category scale ranged from ‘excellent’(10) to ‘unbearable’ (1). In the second part of the experiment, the participants were requested toprovide assessments on multiple 9-point category scales with respect to attributes like ‘powerful’,‘acceptable’, ‘expensive’, ‘tonality’ or ‘sharpness’.
Several product noises were assessed an acceptable or fair sound quality, however a significant partof the kettles obtained only poor, very poor or even unbearable sound quality ratings (see fig. 5). As
indicated by the non-overlapping confidence intervals, as expected the different product noises werestatistically significant judged regarding sound quality. The same applies to other evaluation
dimensions as displayed in figure 6.
10SQ assessment(0-unbearable10-excellent)

9876
5
4
32
1
0
DUT2DUT1

DUT6

DUT12

DUT14

DUT7

DUT10

DUT13

DUT4

DUT9

DUT11

DUT8

DUT3

DUT5

Devices under test

Figure 5 – Sound quality assessments (average, 95% confidence interval) of kettles emitting noise duringboiling water (colors indicate quality classes: green: good, yellow: acceptable, orange: insufficient, red: poor)

quiet

robust9,08,0
7,0
6,0
5,0
4,0
3,02,01,0quiet

not sharp

expensiverobust9,08,07,06,05,04,03,02,01,0

not sharp

powerful expensive

not tonal

acceptable

powerful

not tonal

acceptable

Figure 5 – Assessments (average) with respect to different evaluation criteria of kettles emitting noise duringboiling water (left: good devices under tests, right: poor devices under test)
The case study illustrated that the acoustical and perceptual differences of consumer products on
the market (like kettles) can be great. It has to be pointed out that the noise of kettles judged as poor did
not universally possess more power reducing the time needed to boil the defined amount of water. Bymeans of additional (psychoacoustic) parameters the sound character can be predicted. The term‘sound character’ refers to the perception related to basic sensory attributes of auditory events without
considering context effects (like influences like design, haptics, brand name, etc. on the assessment of8007

product sound). The detailed description of the sound character of a product noise might be more amore meaningful information related to perception than sound power level information only. However,
it is challenging to develop a format which will be understandable for consumers and help them tomake better informed purchasing choices.

5. CONCLUSIONS
It is evident that noise emissions are an issue in industry, in communities, in buildings, and during
leisure activities [5]. In the context of products noise classification several national and international
activities are evidence of the increasing social interest in environmentally-friendly products andtechnologies. So far, motivation to purchase environmentally-friendly products is only partiallyachieved by recent action and initiatives. In most cases, only some minimum requirements are defined,
which are not stimulating more extensive sound design efforts. In most cases, only the emission isconsidered instead of the typical receiver/operator perspective (immission). Unfortunately, several
eco-labels are not enforced and companies can voluntarily apply for. It is expected that it is even notnecessary to enforce quiet product noises by law, in case a sound (quality) label indicating quiet
recommendable products is acknowledged by consumers. In this case, it will be attractive for
manufacturers to optimize sound quality and to highlight the respective acoustic comfort level of theproduct, which will influence purchase decisions.

REFERENCES
1. Schwela D. Noise of consumer products: Consequences for environmental health, Noise NewsInternational, Vol.14 (3), 102-111, 2006
2. German Federal Ministry for the Environment, Nature Conservation and Nuclear Safety.
Umweltbewusstsein in Deutschland 2016. Ergebnisse einer repräsentativen Bevölkerungsumfrage, 2017
3. World Health Organization. Noise guidelines for the European Region, Copenhagen, Denmark, 2018
4. World Health Organization. Preamble to the Constitution of the World Health Organization as adopted
by the International Health Conference, New York, 22 June 1946, Geneva, 1946
5. National Academy of Engineering. Technology for a quieter America, The National Academies Press,2010
6.Council Directive 92/75 EEC. On the indication by labelling and standard product information of theconsumption of energy and other resources by household appliances, 22 Sep. 1992
7. European Commission. New energy efficiency labels explained. Fact sheet, Brussels, 11 March, 2019
8. Merriam-Webster Online Dictionary, 31 May, 2019
9. Lang W. Quieting the world by fostering a "Buy Quiet" attitude among product purchasers, Noise NewsInternational, Vol. 19 (3), 86-106, 2011
10. Council Regulation (EEC) No 880/92. On a community eco-label award scheme, 23 March 1992, 1992
11. Fabris C. Labeling of product noise, Proc. Noisecon 2016, Providence, USA, 2016
12. ISO 532-1. Acoustics. Methods for calculating loudness. Part 1: Zwicker method, International
Standardization Organization, Geneva, Switzerland, 201713. DIN 45692. Measurement technique for the simulation of the auditory sensation of sharpness,
Deutsches Institut für Normung, Beuth Verlag, Germany, 2009
14. Nobile MA, Bienvenue GR. A procedure for determining prominence ratio of discrete tones in noiseemissions, Proc. Noisecon, Tarrytown, USA, 1991

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