Consumers value products that provide a multi-sensory experience. This paper provides a summary of our recent work on the design of sensory experiences using the sound symbolism of onomatopoeia with a focus on the operation of rotary switches. The experiments were conducted to collect onomatopoeic expressions that reflect tactile and auditory experiences during switch operation. A quantitative text analysis was conducted to examine the correspondence between these expressions and physical quantities. In the representation of mono-sensory experiences through onomatopoeic expressions, our findings reveal a distinct sound symbolism in onomatopoeic expressions that reflects changes in physical quantities such as click torque for tactile sensations and sound loudness and sharpness for auditory sensations. For tactile and auditory multi-sensory experiences, the onomatopoeic expressions incorporate features of both sensations. Moreover, the results suggest that when tactile and auditory stimuli are combined, the sharpness of the operating sound has the most influence on onomatopoeic expressions. These insights suggest the potential of using the sound symbolism of onomatopoeia for quantitatively designing sensory experiences. This approach could be used to capture consumer intent and incorporate qualitative experiences into product design.

Elastic modulus of granular materials consisting of non-adhered solid grains depends on its compressive stress. As vertical compressive stress increases with depth due to gravity without any additional force, the elastic modulus of granular materials also increases along the gravitational direction. This study investigates the sound absorbing characteristics of granular materials with such gradient elasticity for both vertical and horizontal sound propagations, considering applications to vertical walls, horizontal ceilings, and floors. The normal incidence sound absorption coefficients of hollow glass beads, chosen as a representative granular material, were measured using an impedance tube. This measurement was conducted under conditions where the sound wave propagated perpendicular and parallel to the gradient direction of elasticity. The frequency and magnitude of the first peak in the sound absorption coefficient varied with the direction of sound propagation. A method for predicting this variation was proposed, showing that the frequency at which the first peak occurred could be predicted within an error of 10%. Additionally, the effects of the thickness and shape of the absorbing surface on the sound absorption coefficients are elucidated through calculations.

Perfectly diffuse sound fields can be modeled by using an infinite number of random coefficients of spherical wave functions or random plane waves. The statistical properties of the spherical harmonic coefficients and the plane-wave amplitudes in these models directionally define the perfect diffuseness, yielding the established theoretical formulations of directionally characterized perfect diffuseness. However, sound fields in real rooms are not perfectly diffuse. These models and formulations of perfect diffuseness thus provide limited insight into understanding pseudo-perfect diffuseness, the diffuseness of real sound fields. This requires a theory that efficaciously describes pseudo-perfectly diffuse sound fields. Here, we rigorously compare existing formulations of directionally characterized pseudo-perfect diffuseness, aiming to determine its better formulation for the diffuseness evaluations of real sound fields. Our theoretical and numerical results indicate the advantages of the formulation using random coefficients of truncated- or finite-degree spherical wave functions over the formulation using a finite number of random plane waves.

This study explores the impact of pinna hardness and vibrator placement on the efficacy of bone conduction through the pinna. Hearing thresholds of twelve participants, all without abnormal pinna conditions, were assessed across frequencies ranging from 250 Hz to 8 kHz, with vibrators positioned at three distinct locations—the front of the ear canal, the earlobe, and behind the cymba concha. Additionally, with a focus on consistent variable manipulation in a controlled experimental scenario, four silicone ear models with Shore hardness values from 0A to 45A were utilized to examine vibrational energy transmission via an accelerometer fixed behind the ear canal. The results indicated that vibrator placement significantly influenced hearing thresholds, a pattern that was also observed in the silicone models. However, the anticipated correlation between pinna hardness and hearing thresholds was not significant within the human sample. This could be attributed to less variability in natural pinna hardness than expected. While it is recognized that pinna hardness varies among individuals, our study reveals a less dramatic variation in pinna hardness among individuals, suggesting that its influence on bone conduction may be less critical than other anatomical factors.

In this study, the assessment of musical performances is investigated, focusing particularly on the difference between performers' self- and external assessments. Understanding the difference is significant for both the improvement of teaching methods in musical education and the early detection of musician's dystonia. The research centers on brass instrument players performing long tones, a simple task that reduces skill-based performance variances. Additionally, it incorporates Go/No-go tasks to minimize assessment biases. The results reveal a notable discrepancy between performers' and third parties' assessments. We assume that the reasons are the difference in information and the decreased perceptual accuracy of the performers.

Human speaker recognition performance can be degraded by various factors. Understanding the factors affecting it and the errors caused by these factors is crucial for forensic applications. To study the effects of noisy environments on human speaker recognition, we conducted a hearing experiment using speech samples of two words by five male speakers, and two noise types (speech-like noise and environmental noise in boiler room) with three steps of signal-to-noise ratio (∞, 0 dB, or −10 dB). The results suggested that the listeners tended to observe different speakers to be the same speaker rather than vice versa, and this tendency was also affected by sex of the listener.

Cicadas sound loudly and interfere with traffic noise measurements. The frequency characteristics of some outdoors cicada sounds have been reported, but the background noise and distance to the cicada have not been considered. The aim of this work was to accurately measure the frequency characteristics of the A-weighted sound pressure level of each robust cicada sound. The frequency characteristics of the /mi/ and /n/ sounds were measured in a free field. The dominant frequencies were 4.7 kHz for the /mi/ sound and 15 kHz for the /n/ sound, and the distributions of the peak frequencies for their sounds were normal.

The medial olivocochlear reflex (MOCR) is reported to be modulated by the predictability of an upcoming sound occurrence. Here the relationship between MOCR and internal confidence in temporal anticipation evaluated by reaction time (RT) was examined. The timing predictability of the MOCR elicitor was manipulated by adding jitters to preceding sounds. MOCR strength/RT unchanged in a small (10%) jitter condition, and decrease/increase significantly in the largest (40%) jitter condition compared to the without-jitter condition. The similarity indicates that the MOCR strength reflects confidence in anticipation, and that the predictive control of MOCR and response execution share a common neural mechanism.

Binaural and transaural systems are well-known methods of sound field reproduction. However, each system has its own problems such as in-head localization and narrow control points. Therefore, this study aims to design a sound field reproduction system using shoulder-mounted wearable-speakers that can solve these problems. The system is expected to sustain the effect of sound field reproduction even while moving and is expected to be applied in the field of entertainment. This paper shows the head transfer function of the wearable loudspeaker and designs an inverse filter, which is indispensable for the sound field reproduction system, using H_∞ control theory.

The irrelevant speech effect (ISE) depends on psychoacoustic features such as the perceived fluctuation of the sound. Thus, it seems likely that a hearing loss may also affect the amount of the ISE. The present experiment studied the ISE in 30 listeners with normal hearing and 30 listeners with self-reported hearing loss in four different background sounds: speech, music with vocals, instrumental music without lyrics, steady noise. As expected, short-term memory performance increased in that order for both groups. However, there was no statistically significant interaction between the two groups, both memorized 0.9 digits more in noise than in speech.