PSYCHOLOGICAL PROCESS IN SENSORY EVALUATION ON ODORS FROM BUILDING MATERIAL

Akihisa Takemura 1†, Toshio Yamanaka 1, Hisashi Kotani 1, and Takeshi Tomita 2

1Department of Architectural Engineering, Graduate School of Engineering, Osaka University, Japan

2Kajima Corporation, Japan ABSTRACT There are a lot of aspects for evaluation of odor. Not only the hedonics aspects but also the pleasantness aspects are very important for the building design. Authors have investigated the sensory evaluation of odor from building materials and turned our attentions to the psychological process of odor evaluation. In this paper, odors emitted from four building materials that is wood, wood flooring, Tatami (Japanese traditional rush mat) and concrete were adopted and the sensory evaluation tests by human subjects were conducted. Odor intensity, hedonics, preference and acceptability were voted by ten young subjects. The impressions of odor represented by familiarity, freshness, complexity and warmness were evaluated as well. The correlations of each evaluation were investigated and tried to make a model of the psychological process of sensory evaluation by means of multiple regression analysis. As a result, odor acceptability was proved to be largely influenced by odor intensity, secondly the hedonics of odor led the evaluation of acceptability. Odor impressions decide the hedonics of odor, and especially the familiarity and complexity were proved to be the important factors. KEYWORDS Odor, Sensory evaluation, Psychological process, Tatami, Acceptability INTRODUCTION People spend long time indoors. The odor from the building materials is supposed to have a large effect on judging the quality of the indoor environment. In this study, the effect of the odor from the building materials on the sensory evaluation of the person in a room is investigated for the purpose of helping a better indoor environment design. To design the indoor environment, it is important to reveal the relation between the odor concentration and the odor sensation. The relation between the odor dilution factor and acceptability about the nylon carpet, linoleum, polyolefine and sealant was investigated. (Knudsen (1998)) The impact of temperature and humidity on odor intensity and acceptability was investigated about the PVC flooring, carpet, floor varnish, wall paint and sealant.(Fang (1998a,b)) It is, however, necessary to investigate the detailed structure of sensory evaluation.

In this paper the relation between the odor concentration and the five aspects that are intensity, hedonics, preference, impression and acceptability is discussed. The relation between each aspect is also investigated. The psychological process of sensory evaluation was investigated, based on the result of multiple regression analysis. METHOD Subjects Ten male subjects between the age of 22 and 26 years old had passed “the T&T olfactometer”, which was used as subjects of sensory evaluation test in Japan.

† Corresponding Author: Tel: + 816 6879 7645, Fax: + 816 6879 7646 E-mail address: takemura_akihisa@arch.eng.osaka-u.ac.jp

Samples Five building materials which were two types of woods, wood flooring, Tatami (Japanese traditional rush mat) and concrete were selected because they were generally used in buildings. The white cedar from conifers and oak from broadleaf trees were used as woods. F three star grade of wood flooring was selected. (It is the former standard of JAS Fc0; the criteria emission is lower 0.5mg/L (average), 0.7mg/L about formaldehyde) Concrete was poured with water of 150cc in order to assume the condition of rain.

Method Each sample was put into the airtight chamber in which the air was mixed inside it. One hour later, the sampling odor was extracted into the sampling bag by the fleks pump; which has a noncontact structure between the sampling odor and the pump, and is often used in odor experiments in Japan. The sampling bags were set in the chamber in order to avoid infiltration (see Fig.1). The sampling odor was diluted by the three times (1, 3, 10, 30, 100 and only for the white cedar, 300) into the odor bag. Consequently 26 pieces of the odor bag were prepared in all.

Procedure The experimental procedure is shown in Fig.2. Subjects were given the instruction before the start of the each experiment. Subjects smelled 26 odor bags in random order for one experiment. The sensory evaluation scales are shown in Table1. The scale of intensity was the six point scale as the interval scale which is derived from Ohsako (1991). The scales of hedonics and preference were the nine point scale. About impression, the seven point scales were selected as suitable for the four factors; familiarity, freshness, complexity and warmness which had been investigated in Tomita (2001). About acceptability, subjects were requested to answer whether they would accept the odor or not if they stayed in a room filled with it for a long time. After sensory evaluation, the sampling odor concentration of each sample was measured according to “the triangle odor bag method”. The experiment was conducted three times.

RESULTS From the result of the triangle odor bag method，the odor thresholds and odor concentrations were determined as the geometric mean of the concentrations of three times experiments. (see Table2)

Table 1 Scales for sensory evaluation scale

Figure 1. Odor extracting method

Table 2 Odor concentration of each case

Figure 2. Experimental procedure

About sensory evaluation value, 2 tops and bottoms of the 10 evaluation value were cut and 6 evaluation value of each three time experiment was summed up，That is 18 sensory evaluation value was used. Relation between odor concentration and each evaluation Fig.3 shows relation between odor concentration and five aspects of sensory evaluation which are intensity，hedonics，preference，impressions (familiarity, freshness, complexity and warmness) and acceptability about five samples. In Fig.3, the frequency of evaluations is expressed as areas of a circle, and the median values of evaluations as lines. In the part of intensity, the regression lines of the average values by least square method are shown as bold lines. In the part of the acceptability, two regression curve by the logit model for each sample (solid line) and for kitchen garbage (by Mitsuda (1996))(dotted line) were shown. (1) Intensity It is found that the intensity increases with increasing the odor concentration. The regression line is consistent with 50 percentile plot line in all cases. It can be said that intensity is proportional to the logarithm of odor concentration. The slope of the regression line is different for each case. (2) Hedonics and preference It is found that the hedonics decreases with increasing the odor concentration in the case of white cedar, oak, Tatami and concrete. This tendency is opposite in the case of wood flooring. It is found that the tendency of preference evaluation is similar to the hedonics. (3) Impressions It is found that the familiarity decreases with increasing the odor concentration in the cases of white cedar，oak，Tatami and concrete. The relation is opposite in the case of wood flooring. This tendency is

Figure 3. Relation between odor concentration and five aspects

almost the same as ones of hedonics and preference. It is found that freshness and complexity increase with increasing odor concentration in all cases. The complexity of Tatami is higher than the other cases. It is found that warmness is not so much related to the odor concentration. (4) Acceptability It is found that the percentage of person unaccepted increases with increasing odor concentration in all cases. In the case of wood flooring, the percentage of person unaccepted is low in high concentration. In the case of Tatami the percentage of person unaccepted is high in low concentration. The logit model would apply to the cases of white cedar, oak and concrete. It is necessary to store more data in order to apply the logit model to the case of Tatami. The case of concrete is much similar to that of kitchen garbage. In the cases of white cedar and oak, the percentage of person unaccepted is lower than that in the case of kitchen garbage in the same concentration.

Relation between evaluations Relations between each evaluation are shown in Fig.4 to Fig.7. The frequency of evaluations is expressed in areas of a circle, and the correlation coefficient is shown in the figures. Figures are shown by the 30 evaluation values which are not cut. (1) Relation between intensity, hedonics and preference Fig.4 shows relation between intensity and hedonics for five samples. There is negative and strong correlation in Tatami. There is negative and slightly strong correlation in the case of concrete. Relation between intensity and preference shows the same tendency as relation of intensity and hedonics, therefore the figure is omitted. Fig.5 shows relation between hedonics and preference for five samples. There is positive and very strong correlation in all cases.

Figure 4. Relation between intensity and hedonics

Figure 5. Relation between preference and hedonics (2) Relation between intensity, hedonics and preference and impressions Fig.6 shows relation between intensity and familiarity which is one factor of the impression, for five samples. There is positive and strong correlation in the case of Tatami. There is positive and slightly strong correlation in concrete. About relation between freshness and intensity, there is positive and slightly strong correlation in white cedar and wood flooring.

About relation between complexity and intensity and that of warmness and intensity, there is little correlation in all cases (The figures are omitted about freshness, complexity and warmness.). Fig.7 shows relation between familiarity and hedonics for five samples. There is positive and very strong correlation in all cases. About the relation between freshness and hedonics, there is positive and slightly strong correlation in oak, wood flooring and concrete. About relation between complexity and hedonics, there is no correlation in all cases. About relation between warmness and hedonics，there is positive and slightly strong correlation in wood flooring and concrete (figures are omitted about freshness, complexity and warmness.). Relation between impression and preference shows almost the same tendency as relation between impression and hedonics, the figure is omitted.

Figure 6. Relation between intensity and familiarity

Figure 7. Relation between familiarity and hedonics

Figure 8. Relation between intensity and acceptability (3) Relation between acceptability and intensity, hedonics, preference and impression It was indicated that intensity is proportional to the logarithm of odor concentration and that the logit model can apply to the relation between acceptability and odor concentration. From these results, the equations shown in Fig.8 are derived, which is the logit model of the relation between acceptability and intensity. Fig.8 is expressed by the average plots of 18 sensory evaluation value which 2 tops and bottoms from the 10 evaluation values were cut and 6 evaluation values of each three times

experiments were summed. The logit model can apply to this correlation. Therefore it can be said that the percentage of person unaccepted can be predicted from the evaluation of intensity, without measuring odor concentration. Fig.9 shows relation between acceptability and familiarity. There is a decrease in the percentage of person unaccepted decreases with increase of familiarity in all cases. About relation between acceptability and complexity, there is a increase in the percentage of person unaccepted increases with increase of complexity in all cases. About relation between acceptability and freshness and relation between acceptability and warmness, there is no correlation in all cases. The figures about freshness, complexity and warmness were omitted.

Figure 9. Relation between familiarity and acceptability Fig.10 shows relation between acceptability and hedonics. There is a decrease in the percentage of person unaccepted with increasing hedonics in all cases. The relation between acceptability and preference shows similar tendency as this result (the figures are omitted).

Figure 10. Relation between hedonics and acceptability

DISCUSSION Psychological Process of Sensory Evaluation The psychological process of sensory evaluation was investigated from results above mentioned. The procedure is as follows (see Fig12). (1) Assumed that the quality of odor is made from odor concentration and selection of building material. (2) Acceptability was considered as the final evaluation. (3) Preference was considered as nearly equal to hedonics. (4) It was investigated where intensity, hedonics and impressions are located between (1) and (2), by the means of multiple regression analysis. Here, the evaluation scales for this investigation are necessary to be an interval scale because of analyzing by the multiple regression method. It was investigated that the scales of intensity, hedonics, preference and impressions are equal interval by the method of successive categories. Fig.11 shows the relation between primary category scale and theoretical interval scale by method of successive

categories, and the correlation coefficient between them. All values of the correlation coefficient are almost 1. Although in the scale of intensity the line becomes gentle with increasing primary scale, the scales of intensity, hedonics, preference and impressions can be considered as interval scales. Two steps of multiple regression analysis were conducted as follows. (5) Acceptability was adapted as a target variable, intensity and hedonics as an explanatory variable. ((a) in Fig.12) (6) Hedonics was adapted as a target variable, impressions as an explanatory variable. ((b) in Fig.12) Fig.12 shows a model of the psychological process of sensory evaluation based on these results. The standard partial regression coefficients are shown in the figure. Acceptability is determined by intensity and hedonics with the ratio about 6:5. Impressions which are

Figure 11. Relation between primary category and theoretical interval scale

Figure 12. A model of the psychological process of sensory evaluation (Value shows the standard partial regression coefficient, and number with parenthesis shows the procedure of investigation.)

(1)

(2)

(3) (4)

(5)

(6)

familiarity, freshness, complexity and warmness determine hedonics with the ratios about 6:2:5:2. CONCLUSIONS ●Relation between odor concentration and sensory evaluations of odor from building materials ・Intensity was proportional to the logarithm of odor concentration. The slope of the regression line was

different from each material. ・Hedonics, preference and familiarity decrease with increasing the odor concentration in white cedar,

oak, Tatami and concrete. The relation is reversed in wood flooring. ・Freshness and complexity increases with increasing odor concentration in all cases. ・Warmness is not so much related to the odor concentration. ・The percentage of person unaccepted increases with increasing odor concentration in all cases, and

the logit model would apply to white cedar, oak and concrete. ●The relation between sensory evaluations ・Intensity and hedonics; negative correlation was seen in Tatami and concrete. ・Preference and hedonics; positive and very strong correlation was seen in all materials. ・Intensity and familiarity; positive correlation was seen in Tatami and concrete. ・Familiarity and hedonics; positive and very strong correlation was seen in all cases. ・Freshness and hedonics; positive correlation was seen in oak, wood flooring and concrete. ・Complexity and hedonics; no correlation was seen in all cases. ・Warmness and hedonics; positive correlation was seen in wood flooring and concrete. ・Intensity and acceptability; the percentage of person unaccepted increases with increasing intensity in

all cases. The logit model can apply to this correlation. Therefore it could be said that the percentage of person unaccepted was predicted from the measurement of intensity, without measuring odor concentration.

・Familiarity and acceptability; the percentage of person unaccepted decreased with increasing familiarity in all cases.

・Freshness and acceptability; no correlation was seen in all materials. ・Complexity and acceptability; the percentage of person unaccepted increased with increasing

complexity in all materials. ・Warmness and acceptability; no correlation was seen in all materials. ・Hedonics and acceptability; the percentage of person unaccepted decreased with increasing hedonics

in all materials. ●Consequently, a model of the psychological process of sensory evaluation was shown. REFERENCES 1. H.N.Knudsen O.Valbjorn P.A.Nielsen (1998)“Determination of Exposure-Response Relationships

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