# Validation of the Developed Psychoacoustic Model for Sound Quality Valuation of Washing Machines
## 1 Introduction  
Sound has many objectively measurable properties, but they may not provide a clear picture of what a person actually captures with their ears. Psychoacoustics is a scientific field that researches human perception of sound. Unlike general acoustics, in which we use microphones or other devices that can be calibrated to obtain data, in psychoacoustics, the only relevant \"measuring tool\" is the person themselves. According to [1, 2, 3], in addition to its intensity, it is necessary to include other subjective parameters such as environmental conditions and psychoacoustic parameters (loudness, sharpness, roughness, fluctuation strength, and tonality) in the evaluation of sound quality. In psychoacoustics, various psychophysical methods are used to evaluate soundquality [4; 5]. The most famous psychophysical law is the \"Fechner law\", which states that with a geometric increase in the intensity of the stimulus, the subjective perception of the stimulus increases arithmetically. However, in the professional literature, we can more often find it under the name \"the Weber-Fechner law\" [6; 7]. The authors' [8] research examines the effectiveness of the acoustic metawindow unit (AMW) in terms of psychoacoustics and human perception. Subsequently, they combined soundscape-based questionnaires with an analytical physical and psychoacoustic evaluation of the AMW. Psychoacoustics [1; 9; 10; 11] is a powerful tool for optimizing the acoustic properties of sound in machines, equipment, and products in industry. It is used to better understand how people perceive sound. In connection with the application of psychoacoustics in practice, a new scientific field of sound (acoustic) product design was created. Reducing the noise level of household appliances such as washing machines [12; 13; 14], dishwashers [15], refrigerators [16], hair dryers [17], vacuum cleaners [18], air conditioners [19; 20], range hoods [21], etc., has become a top priority for manufacturers due to increased user demand for such products. Noise has become one of the important factors in purchasing decisions. However, noise reduction methods can be expensive and difficult to use, forcing manufacturers to compromise on their effectiveness, longevity, and cost. The sound quality index is one of the parameters that describes the acoustic quality of products. Most research papers examining the evaluation of the sound quality index of household appliances are based on a regression model that considers multiple linear regression between the results of subjective evaluation and psychoacoustic properties. This issue has been examined by several authors [3; 16; 22; 23; 24; 25]. The authors [25] focused their research on a product-neutral approach, based on solutions to reduce the overall sound power level under different operating conditions (under IEC60704 guidelines) of a front-loading washer-dryer. The aim of the study [13] was to predict the sound quality perception of prefilled washing machines using neural networks. The pleasantness/annoyance of the sounds of the washing machine was assessed by the participants using a listening test. Based on the measurement and analysis of the sound emitted by the washing machine, the authors [26] identified critical places with the highest sound levels. The authors [27] constructed a mathematical model based on objective and subjective evaluations of sound quality. The created model turned out to be reliable for predicting human perception of the evaluated sounds of washing machines. [PERSON], et al. [28] developed an experimental methodology to describe noise transmission pathways in a washing machine. In their research, they used intensity probes and vibration acceleration sensors for measurements. The sound quality index, which predicts the subjective score, was proposed in [29]. It is the result of the correlation and multiple regression analysis of the psychoacoustic parameters and subjective assessments of 30 types of refrigerators. [PERSON] et al.