The mean scatterer spacing (MSS) has been identified as an important parameter for characterizing human tissues presenting a semi-regular lattice texture. Most of the work in this area involves the uses of an estimated power spectrum density (PSD) of an autoregressive (AR) model to deduce the MSS from backscattered ultrasonic signals. In this paper, we propose a new method of MSS estimation using the third and fourth-order cumulants, named here TFOCs, of the AR parametric model. The results obtained by this new method is compared with those obtained using PSD.
Perceptual characteristics of broken and drop tones in the Vietnamese language are studied. A broken tone syllable has a glottal constriction at the middle part, while a drop tone syllable has a glottal stop at the end and has a short length. In this study, four experiments were conducted. First, expanding from our previous research, the power control for the broken tone was evaluated using several power patterns and its effectiveness was reconfirmed. The power dip pattern makes the synthetic sound of the broken tone highly intelligible. Second, the similarity between the drop tone and the first half of the broken tone were studied. Experimental results showed that they are comparable, i.e., the first half of the broken tone can be replaced by the drop tone, and the first half of the broken tone can be perceived as a drop tone. In the third and fourth experiments, the final parts of drop and broken tones were examined using different fundamental frequency (F0) patterns. As a result, we found that the drop tone has a perceptual threshold with an F0 slope, while F0 of the final part of the broken tone has a minor effect on its perception.
This Technical Report presents air conduction hearing thresholds measured for pure tones at conventional audiometric frequencies (CAFs) from 125 Hz to 8 kHz and extended high frequencies (EHFs) from 8 kHz to 16 kHz, using apparatus and procedures in accordance with relevant ISO and IEC standards. The subjects were 490 otologically normal Japanese adults aged 18–83 years. Descriptive statistics of their threshold levels are presented in graphical and tabular forms to show the age-related decline of hearing sensitivity and its individual differences. The change in hearing sensitivity of older adults at CAFs was smaller, in general, than the standard values according to ISO 7029:2000, in which the amount of hearing sensitivity decline is estimated as a function of age. The threshold data presented in this report may serve as a basis for revising the international standard. In addition, measurement results at EHFs revealed that the responses of older subjects could be unreliable at the highest frequencies because of an unwanted sound in a lower frequency region generated with test tone presentation. Threshold values at extended high frequencies should be treated with caution.