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Technology for sensory impairments (vision and hearing)
Published in Alex Mihailidis, Roger Smith, Rehabilitation Engineering, 2023
J. A. Brabyn, H. Levitt, J.A. Miele
A fundamental limitation of inductive loop systems is that the audio signal in a telecoil is induced by audio-frequency fluctuations of the EM field. This is not the most reliable method of wireless signal transmission. Other methods of wireless communication use a high-frequency carrier signal that is modulated by the low-frequency audio signal. Radio broadcasting began with amplitude modulated (AM) carrier signals. Distortions of the EM field by sunspots, static electricity in the atmosphere, and other sources of EM distortion caused fading, static interference, and other distortions of AM radio signals. Wideband frequency modulation (FM) was invented by Edwin Armstrong in the 1930s. A wideband FM transmission not only transmits wideband audio signals with high fidelity, but it is also much less susceptible to distortions of the EM medium. Although Armstrong patented his invention in 1933, legal challenges to his patent delayed the implementation of FM radio transmissions for many years. Hearing aids with FM wireless links were developed in the 1950s. These were body-worn instruments because of the relatively large size of FM transmitters/receivers at the time. They were used primarily at schools for the deaf where cosmetic acceptability is not of overriding importance.
Perceptual Speech Coding
Published in Randy Goldberg, Lance Riek, A Practical Handbook of Speech Coders, 2019
Wideband perceptual coding (bandwidth of approximately 20 kHz) is used in audio coding in standards such as MPEG-2 and MPEG-4. The duration of the analysis window used in these wideband coding techniques is around 10 ms [82, 12, 83]. The reciprocal relation between time and frequency dictates that a frequency resolution of only 100 Hz can be obtained using standard frequency-domain transforms (discrete Fourier transform) for this time resolution (10 ms). Here, the frequency resolution refers to the frequency spacing between samples of the DFT. Given this frequency resolution, it is possible to locate regions of simultaneous masking in frequency at high frequencies (i.e., above 5kHz) using the type of data in Figure 6.4. Significant economies in coding can be achieved with frequency domain analysis for wideband audio signals. However, for the lower frequency regions of signals, a much higher frequency resolution is required to exploit the masking properties of the human auditory system. This results from the much narrower frequency spacing of the critical bands at low frequencies.
Voice Transmission
Published in Goff Hill, The Cable and Telecommunications Professionals' Reference, 2012
Stuart D. Walker, Rouzbeh Razavi
Voice over Internet Protocol (VoIP) is a revolutionary technology that enables the use of packet-switched networks to deliver voice traffic. Examples of considerations in designing good VoIP systems include voice quality, latency, jitter, packet loss performance, and packetization. Today′s VoIP product offerings typically include G.711, G.729, and G.722, in addition to G.723.1, where the latter is often favored for videophone applications. G.711 coders are mainly known for their low complexity and delay while resulting in toll-quality voice. Appendix I in G.711 defines a Packet Loss Concealment (PLC) algorithm to help hide transmission losses in a packetized network. G.729, on the other hand, provides a toll-quality voice with acceptable delay level but at the lower rate. G.729 operates at 8 kbit/s, but there are extensions that provide 6.4 kbit/s and 11.8 kbit/s rates. G.722 is an ITU standard codec that provides 7-kHz wideband audio at datarates from 48 to 64 kbit/s. This is especially useful in fixed-network VoIP applications, where the required bandwidth is typically not prohibitive. G.722 provides a significant improvement in speech quality compared to other narrowband codecs such as G.711. Finally, G.723.1 can operate at 6.3 kbit/s (using 24-byte frames) or at 5.3 kbit/s by using 20-byte frames.
A SILK Adaptive Steganographic Scheme Based on Minimizing Distortion in Pitch Domain
Published in IETE Technical Review, 2021
Yanzhen Ren, Shan Zhong, Weiping Tu, Hanyi Yang, Lina Wang
Steganography is a technique that hides secret message in digital carriers for covert communication without arousing any suspicion [1]. As a countermeasure of steganography, steganalysis aims to detect the existence of secret message in those carriers [2]. With the popularity of VOIP and instant voice chat in social application, SILK-compressed audio is widely used in Internet voice communication, such as Skype, WeChat, and Steam game platform. SILK speech codec [3] was first developed by Skype Limited and then incorporated into the Internet Engineering Task Force (IETF) as part of Opus codec, which is the standard of a new Internet wideband audio codec. The codec technology is based on Code Excited Linear Prediction (CELP) framework, combined with the coding principle of iLBC and Speex codec. It is an adaptive coding technology with high coding efficiency in low-rate network environment.
A novel design of low-cost hearing aid devices using an efficient lifting filter bank with a modified variable filter
Published in Expert Review of Medical Devices, 2022
N Subbulakshmi, R Manimegalai, G Rajakumar, T Ananth Kumar, Umadevi Kosuri
Then, the update operation produces even samples later taken into the prediction process to produce different odd samples for the next step. Several investigations have been carried out on various filter bank algorithms. Frequency-warped signal processing techniques are the beginning of wideband audio signal processing development. The modified variable filter bank (MVFB) structure is stated. It is designed to compensate a variety of earshot losses. The device consists of a microphone as an input to process various signals through a signal conditioning unit and output speaker.
Analysis of the application of college popular music education relying on the elite teaching optimization algorithm
Published in Applied Artificial Intelligence, 2023
The new high-fidelity wideband audio coding algorithm belongs to transform coding, and also faces the problem of pre-echo. Based on the analysis of the pre-echo generation mechanism, a new pre-echo processing method is proposed in this paper.