Charturong Tantibundhit

Joint Time–Frequency Segmentation Algorithm for Transient Speech Decomposition and Speech Enhancement

We develop an algorithm, the joint time-frequency segmentation algorithm, where the wavelet packet coefficients of the analyzed speech signal are represented as tiles of a time-frequency representation adapted to the characteristics of the signal itself. Further, our algorithm enables the decomposition of the speech signal into transient and non-transient components, respectively. Any block of wavelet packet coefficients, whose tiling height is larger than or equal to the tiling width belongs to the transient component and vice versa for the non-transient component. The transient component is selectively amplified and recombined with the original speech to generate the modified speech with energy adjusted to be equal to the original speech. The intelligibility of the original and modified speech is evaluated by 16 human listeners. Word recognition rate results show that the modified speech significantly improves speech intelligibility in background noise, i.e., by 10% absolute at 0 dB to 27% absolute at -30 dB.

An improved proof for RFID tags

An RFID system consists of an RFID reader, a server connected to a database, and RFID tags attached to the objects needed to be identified. We are interested in the case where two tags are needed to be simultaneously scanned in a readerpsilas field, for which many protocols have been proposed in literature. They however are all insecure for the special case, where an adversary, acting as a reader, can penetrate the server and access data stored in the server. In this paper, we propose a protocol to remedy this problem for two-tag environment. In addition, it can be extended to more-than-two-tag environment without much increasing total amount of time to scan all the tags.

A novel anti-collision algorithm for high-density RFID tags

In a radio frequency identification (RFID) system, when more than one tag communicates with a reader at the same time, a collision will occur resulting in the failure of that communication. Many anti-collision algorithms, such as Binary Tree (BT), FSA, and DFSA have been used in ISO and EPC standards to prevent such a collision. This paper develops a new anti-collision algorithm based on the BT and the DFSA algorithms. Specifically, all tags are divided into many groups using the DSFA algorithm. Then, the tags in each group are identified using the BT algorithm. Results indicate that the proposed algorithm performs better than the existing ones in terms of the number of used time slots (the less the used time slot, the faster the algorithm).

Speech enhancement based on joint time-frequency segmentation

We present an algorithm to decompose speech into transient and non-transient components. Our algorithm, the joint timefrequency segmentation algorithm, uses the wavelet packet coefficients of the speech signal and represents them as tiles of a time-frequency representation adapted to the characteristics of the signal itself. Any wavelet packet coefficient, whose tiling height is larger than or equal to the tiling width is characterized as a transient coefficient and vice versa for the nontransient coefficient. The transient component is selectively amplified and recombined with the original speech to generate the modified speech with energy adjusted to be equal to the energy of the original speech. The psychoacoustic tests performed with fourteen human listeners show that the speech modification significantly improves speech intelligibility in background noise, i.e., for 10% absolute at 0dB to 31% absolute at −30dB.

Automated embolic signal detection using adaptive gain control and classification using ANFIS

This work proposes an automated system for real-time high-accuracy detection of cerebral embolic signals (ES) to couple with transcranial Doppler ultrasound (TCD) devices in diagnosing a risk of stroke. The algorithm employs Adaptive Gain Control (AGC) approach to capture suspected ESs in real-time. Then, Adaptive Wavelet Packet Transform (AWPT) and Fast Fourier Transform (FFT) are used to extract from them features most efficiently representing ES, which determined by Sequential Feature Selection technique. Extracted feature vectors from the suspected ESs are later determined whether they are of an ES or non-ES interval by Adaptive Neuro-Fuzzy Inference System (ANFIS) based classifier. The effectiveness of the developed system was evaluated over 19 subjects going under procedures generating solid and gaseous emboli. The results showed that the proposed algorithm yielded 91.5% sensitivity, 90.0% specificity, and 90.5% accuracy. Cross validations were performed 20 times on both the proposed algorithm and the High Dimensional Model Representation (HDMR) method (the most efficient algorithm to date) and their performances were compared. Paired t-test difference showed that the proposed algorithm outperformed the HDMR method, in both detection accuracy [t(19, 0.01) = 132.2073, p ~ 0] and sensitivity [t(19, 0.01) = 131.4676, p ~ 0] at 90.0% specificity, suggesting promising potential as a medical support system in ES monitoring of various clinical settings.

Perception of Thai distinctive vowel length in noise

A forced choice identification perception experiment using 150 monosyllabic rhyming-word stimulus pairs (with identical consonants and tone) in four conditions of white Gaussian noise was conducted to explore vowel confusions in Thai, a language with nine monophthongs and length (short-long) contrast for all vowels (e.g., /i/-/i:/ and /o/-/o:/). Each stimulus containing speech and noise portions is equal in length. Perceptual results of 18 vowels from 36 Thai listeners at a noise level (SNR) of -24 dB, where the percent intelligibility is the most interpretable, showed that stimuli with short vowels are more accurately perceived than those with long vowels (93.46 vs. 85.64%) with /o:/ and /e:/ as the most confusable. Interestingly, asymmetrical confusions are observed with very few short vowels being misperceived as long vowels, but a larger number of long vowels misperceived as short. Consistent with previous studies of perception of English vowels in white noise [e.g., Benki (2003)], the findings confir...

Performance comparison of the authentication protocols in RFID system

Radio frequency identification (RFID) is a technology for automated identification, which consists of a reading device, a server and RFID tags. We are interested in authentication protocols where two tags are simultaneously scanned by an RFID reader. Although there are several authentication protocols proposed in literature, some of them are insecure. This paper analyses the security of the authentication protocols based on two possible attacks: the brute-force attack against the proof and the forgery attack by using an authorised reader interacting with RFID tags. We also evaluate these protocols in terms of computation costs, communication costs and the resources used by adversary to run the attack (e.g., the size of memories and the number of queries). The results from our analysis indicate that our proposed protocol is more secure than the others and provides a countermeasure against forgery attack.

Development of a Thai phonetically balanced monosyllabic word recognition test: Derivation of phoneme distribution, word list construction, and response evaluations

Abstract This paper proposes a test tool for Thai word recognition, the Thammasat University Phonetically Balanced Word List 2014 (TU PB’14), standardized on several major criteria: phonemic balance, familiarity, reliability, list equivalency, and homogeneity. Phoneme distributions from the largest written Thai corpus (InterBEST) were obtained and used to construct five phonetically balanced word lists, each containing 25 frequently occurring monosyllabic words. Listeners’ percent correct discrimination scores from test and re-test sessions were not significantly different, confirming test reliability. Detailed analysis of listeners’ errors revealed that perceptual errors occurred predominantly for initial sound only, final only, and initial together with final. In terms of list equivalency and homogeneity, derived psychometric function slopes of TU PB’14 ranged from 0.0941 to 0.1155, while intensities required for 50% intelligibility ranged from 41.0279 to 41.3697. Two-way Chi-Square analysis performed on both parameters indicated that there was no significant difference among the word lists.

Role of carrier signal types in perception of Thai phonemes: Implications for cochlear implant recipients

It is well known that segmental (consonants and vowels) and suprasegmental (e.g., tone and stress) speech sounds provide intrinsically different kinds of perceptual information. These differences suggest that phoneme perception might be improved in cochlear implant strategy by employing a carrier signal that is most compatible to each type of speech sounds. However, all speech vocoder strategies for cochlear implant (CI) available in most of works use one carrier signal due to their simplicity to implement. In this paper, we investigated the role of five different carrier signals for Thai speech perception on different types of phonemes, i.e., sine-carrier with/without band-pass filter (TF/TNF), noise-carrier with/without band-pass filter (NF/NNF), and temporal fine structure carrier (TFS). Each type of carrier signal was used to synthesize speech stimuli using the continuous interleaved sampling (CIS) strategy as basic and commonly used for CI. Four different psychoacoustic tests for initials, finals, vo...

Durational and spectral differences in Thai diphthongs and final glides

Acoustic analysis was conducted to compare Thai monophthongs /i, ii, Ɯ, ƜƜ, u, uu, a, aa/, diphthongs /ia, Ɯa, ua/, and vowel-to-glides (vowel + /j/or /w/) in terms of duration, formant frequency, and spectral rate of change (TLroc). Preliminary results from multiple repetitions of 30 target monosyllabic words (from 3 males) show that durational values of long monophthongs are approximately two times as long as the short counterparts. The diphthong onsets (/i/, /Ɯ/, /u/) and offsets (/a/) as part of diphthongs appear to be more centralized than when they occur in monophthongs. Syllables with final glides appear to be longer than those with other final consonants, reducing length differences between syllables with short and long vowels. Interestingly, not only that Thai diphthongs and vowel-to-glides differ in their articulatory trajectories, but they appear to differ in terms of duration and TLroc values. Average duration of diphthongs is shorter than that of vowel-to-glides. TLroc of diphthongs is on ave...