Sound Design Laboratory, Hiroshima City University
Hiroshima City University, Graduate School of Information Sciences, Sound Design LaboratoryLast modified : 31st of January, 2021
・Sound Design for Car Interior Sound
・Active Control of Noise and Sound Quality
・Psychoacoustics
・Body-Conducted Speech Recognition
・Early Detection System to Find Respiratory
・Singer's Formant
・Neurophysiological Index of Uncomfortable Loudness Level
Contact : Shunsuke ISHIMITSU, Dr-Eng, Professor, 
In recent years, sound design has been considered important to adding value to cars. As a factor that attracts drivers to cars, it is important to feel pleasure and excitement during driving. It is considered that sounds generated from automobiles play an important role in these feelings. In this research, we investigated the feeling of excitement with initial sounds when getting into a car to clarify the excitement sense coming from sounds. Sounds in the car involve “open the door,” “close the door,” and “start the engine.” To clarify the feeling in the sound before driving, we conducted an auditory experiment using the semantic differential method. Then, we carried out factor analysis to investigate the relationship between the factor scores and sound characteristics. As a result, it was suggested that anchoring influenced the overall evaluation.
Recent years, rather than the noise measures, the noise gives us the impression even running sound for cars. That is, the control method of the engine sound is shifted from the noise reduction to sound design. Therefore, we proposed a method to design the engine sound using Active Sound Quality Control (ASQC) based on Active Noise Control. Specifically, ASQC involves the algorithm amplifying and reducing the engine specific order components. ASQC was developed to adjust to individual preferences. The individual preferences of sound were connected to each driver’s driving pattern. Thus, we developed an ASQC system, which enables the automatic generation of individual sound preferences.
In recent years, passive noise control (PNC) technology has been employed as a noise reduction method in automobiles. Generally, noise reduction is performed with sound absorbers or sound insulations. Improvement of noise suppression in automobiles has been actively investigated in numerous previous studies. However, there is the possibility that a reduction of the noise level may cause drivers to perceive a greater level of road and the wind noise. Furthermore, automobiles are often used recreationally and described as “Fun to drive" and "Fun to ride." It is certain that some people drive for pleasure and these drivers may experience less enjoyment if the engine sound is reduced by PNC. In addition, engine sound has been shifting from noise reduction to sound design in the production of high-end automobiles. The auditory impression of automobiles with sound absorbers has been investigated.
The sound design of automobiles is one of the factors that affect the attractiveness of automobiles. Even some sounds are more pleasantly, but may have a physical burden. Therefore, we have studied the auditory effect of automobile acceleration sound and auditory impression evaluation with heart rate variability (HRV) analysis to design a comfortable sound environment. First calculation accuracy in HRV analysis was improved using wavelets. Also, the tendency of excitement in auditory impression coincided with the change in sympathetic nerve which extracted by HRV analysis.
The perception of sound is very multidimensional in nature. Among these dimensions, we focus on sound ‘clarity’ whose objective parameter has not yet been specified for spatial impression. To evaluate ‘sound clarity’, an analysis of the physical properties is needed. In this study, the sound clarity of a layout of loudspeakers in a car was investigated and evaluated using transfer functions and time-frequency analyses. Four pairs of loudspeakers were mounted around the driver’s seat. Furthermore, an auditory experiment was conducted to examine the relationship between physical factors and auditory impression. It is believed that the proposed method enables an objective evaluation of sound clarity in car audio systems.
In speech production, people perceive their own voices through their auditory organs and then modulate them through feedback to their vocal organs. This process is called auditory feedback. However, while there have been many studies on auditory feedback for speech, there has not been much research on singing voice. In this study, we have discovered that, as the feedback noise increased, the sound pressure level (SPL) of the singing voice increased. When the participants heard their own voices loudly, their SPL decreased significantly. We have also observed that, when the participants heard their voices with the higher frequencies emphasized, their SPL decreased significantly. Additionally, when a sufficiently high 1st formant frequency was perceived by the auditory organs, the vocal response was decreased.
Today, some audiophiles sometimes discuss the difference of sound quality between different media (e.g. CD, DVD-Audio and internet streaming etc.). Moreover, some manufacturers developed new media to improve these sound qualities. However, any techniques to evaluate sound quality difference between these media are still lacking. We are considering how to check the difference of sound quality difference between media and applicability another musical source with psychoacoustic index.
The UCL (uncomfortable loudness level) is an important factor in hearing aid fitting and the sound design of a notification sound signal. The UCL can be measured by asking for a subjective judgment. As this method requires a great deal of time with loud sounds, a heavy load is applied on participants. An objective UCL estimation method without the load on participants is required. In this study, to construct a neurophysiological index of the UCL, auditory evoked potentials and auditory evoked neuromagnetic response fields (which reflect auditory information processing), and the level dependency characteristics of the brain’s spontaneous magnetic field’s alpha wave (which reflects the comfort of the auditory stimuli) were conducted. The activity of the auditory pathway and UCL-sensitive reactions we re observed.
The pharyngeal tonsil of lymphoid tissue becomes hypertrophied as acquired immunity improves during childhood. Generally, pharyngeal tonsil hypertrophy reaches its peak between the ages of 4 to 6 years, and then the tissue atrophies. However, some cases hypertrophy continues even though the atrophy term has passed have been observed. In these cases, the hypertrophied tissue may lead to sleep and breathing disorders. The many currently available modalities for the detection of pharyngeal hypertrophy are invasive. Therefore, we developed a method for non-invasively detecting pharyngeal tonsil hypertrophy using phonetic sound.
Livestock such as pigs are reared intensively.
Present trends in pig breeding in Japan show that the number of pigs per farm has been on the rise since the 1990s, making efficient livestock management a necessity in this regard.Infectious diseases, especially respiratory diseases, are serious problems in intensive farming.Spreading of diseases in group-housed pigs can lead to death and loss of productivity.Therefore, it is important for pig breeders to detect diseases early.It is difficult to individually detect pigs infected with diseases using microphone, while moving pigs can easily damage the system.We propose an early detection system for respiratory diseases in pigs.The system uses a piezoelectric sensor to record the body-conducted sound of the pigs wirelessly.