Mamoru Iwaki

A Method of High Bit-Rate Data Hiding in Music Using Spline Interpolation

Acoustical signals in digital form can include additional information, this information is separate from the original signal even though they are both stored in a same file. Methods for storing additional information into the original acoustical signal itself have been investigated. Their bit-rate is at most several hundred bit per second. This paper proposes a new method for digital watermarking with higher bit-rate. Its information hiding and detection method is based on spline interpolation. As a result of listening experiment, bit-rate of above 1 kbps was achieved without audible deterioration.

Measurement and adjustment methods of sound source direction perceived through bone-conduction headphones

We investigated the perceived direction of the arrival of sound using bone-conduction headphones. Sounds were separately presented through air-conduction headphones or bone-conduction headphones in a series of experiments and participants judged the direction of arrival. The perceived direction through the bone-conduction headphones inclined toward the center. We propose a design concept to compensate for this discrepancy of the perceived direction of arrival for hearing aids.

A sound recognition method with incrementally taking sound stream into consideration

Domestic sound recognition is an important ability for our daily lives. Although we can recognize sounds as they arrive, conventional automatic sound/speech recognition systems cannot behave in a similar manner. This paper proposes a domestic sound recognition method that can incrementally take sound streams into consideration during the progress of time. This is useful for advancing human-machine interfaces, especially for hearing disabled persons.

A compensation method of sound source direction perceived through bone-conduction headphones by emphasizing interaural level difference

Perceived directions of sound sources presented through bone-conduction (BC) headphones inclined toward the center, rather than air-conduction headphones. Such difference losses some merit of BC headphones as hearing aids. We previously proposed a design concept to compensate the discrepancy of perceived direction of arrival for BC headphones based on emphasis of interaural level difference (ILD). In this study, we have implemented the compensation method and evaluated its performance. As a result, the perceived direction through BC headphones was improved with the proposed ILD emphasis although little difference still remained.

Periodic body sway caused by sound source movement through hearing sensation

Illusory sensations of posture and motion can be perceived in some situations. For example, visually induced self-motion has been studied, while we can demonstrate self-motion and body sway caused by virtually moving sound-sources. We investigated such self-motion and body sway. The center of pressure and the sensation level of self-motion were measured and analyzed to discuss their characteristics in terms of the interaural time difference (ITD) and interaural level difference (ILD) caused by moving sound. As a result, periodic body sway synchronized with sound source movement was observed. Larger ITD and ILD had an influence on self-motion and body sway. In addition, azimuths for ITD and ILD did not need to be matched. Characteristics of auditory induced body sway might be expected to apply for healthcare and fitness fields.

Effect of Visual Stimuli on Temporal Order Judgments of a Sequence of Pure Tones

We investigated what effect visual spatial information had on auditory temporal order judgments (TOJs) and examined what effect visual stimuli had on the TOJs of sequences of pure tones in experiment 1. The auditory stimuli were sequences of four distinct pure tones. The visual stimuli consisted of two vertically aligned flashes: one flashed before the first tone and the other flashed after the last tone. Participants judged whether the temporal order of the second and third tones in auditory stimuli occurred with the higher tone being first or the lower tone being first. As a result, the proportion of responses for higher-tone-first increased when the flash of the upper LED preceded that of the lower LED, independent of the actual temporal order. Participants in experiment 2 were asked to make simultaneity judgments instead, which were also affected by visual stimuli. The auditory stimuli in experiment 3 were the same as those in experiment 1, whereas the visual stimuli consisted of two horizontally aligned flashes. Furthermore, the participants made TOJs, which were not affected by the horizontally aligned visual stimuli. We concluded that vertically aligned visual stimuli had an effect on auditory TOJs with some response bias.

Compensation of sound source direction perceived through consumer-grade bone-conduction headphones by modifying ILD and ITD

When sound stimuli are presented through bone-conduction headphones, the direction of arrival is perceived differently than it is in air-conduction headphones. This paper presents a compensation method in which interaural level difference (ILD) and interaural time difference (ITD) are modified. Experiment results indicate that ILD is more effective than ITD for compensation purposes. This is useful for designing user interfaces in consumer electronics, especially for interfaces for disabled persons.

Emphasizing interaural level difference corrects the shift of perceived direction of sound for consumer-grade bone-conduction headphones

Sounds are perceived not only in air-conduction (AC) manner but also in bone-conduction (BC) one. According to our investigation [Autumn Mtg Acoust. Soc. Japan, 3-1-18, pp. 865-866, 2013; IEEE Int’l Conf. GCCE, pp. 194-197, 2014] about the discrepancy of perceived directions of sound through a BC headphone (TEAC Filltune HP-F200) and an AC headphone (SONY MDR-Z900), the perceived direction through a BC headphone inclined toward the center. In this report, we examined a correction of the shift of perceived direction of sound by emphasizing interaural level difference (ILD). Seven students with normal audibility participated in our experiment. It was carried out in a sound proof room. Sound stimuli were pure-tones of 500 Hz, 1000 Hz, 2000 Hz, and 4000 Hz, with 11 different directions for each stimulus. The sound level through AC headphone was 70 dB. That through BC headphone was adjusted to have the same loudness, for each participant. As a result, the perceived direction through BC headphones was improved....