Portable Audio Devices Research Articles

A silence meant to be heard: LIGNA’s radio ballet

This article analyzes the role of sound in the transformation of social space and organization of noncentered group action through a case study of the series of radio ballets programmed by the German artist collective LIGNA. Typically, LIGNA uses portable audio devices and wireless technology to disseminate instructions to the radio ballet participants, directing them to make synchronized body gestures but not giving them fixed movement paths or identities. This process creates a conceptualized acoustic space parallel to the physical space, challenges the regulations that come with the privatization of public spaces, and dismantles the dichotomies between inside and outside, public and private, and physical and mental. I argue that the radio ballet participants, who form a decentralized, temporary, and mobile community, can explore new possibilities for political intervention in the public sphere through silent collective performances in which sound not only serves the important function of sidestepping visual censorship and avoiding physical conflict but also provides a new methodology for reshaping the order of social space.

Investigation of a new method for sound generation \u2013 Advanced Digital Sound Reconstruction

The current loudspeaker market has a high demand for portable audio devices. Hence, the miniaturization of loudspeakers (microspeakers) is of great importance for manufacturers. Traditional loudspeakers – for example the electrodynamic loudspeaker – are the forerunners, but so-called MEMS loudspeakers (Micro-Electro-Mechanical-System) have emerged recently. MEMS devices have already been used for sensors (i.e., microphones) to a great extend due to their advantages regarding form factor and production efficiency. Albeit additional challenges for actuators like moving enough air with a microstructure – as it is the case for a loudspeaker – the usage of MEMS technology for loudspeakers is very attractive.Since especially low-frequency audio signals often pose problems for microspeakers, this article focuses on a new sound generation technique called Advanced Digital Sound Reconstruction (ADSR) which is especially well-suited for low-frequency audio signals since ADSR can generate more volume displacement relative to its size. Based on a general description of the principle, an outlook of the possibilities regarding achievable sound pressure compared to the classical excitation scheme is derived. Furthermore, measurements are presented, which aim to prove the concept of ADSR based on already existing actuators.

Preserving auditory situation awareness in headphone-distracted persons

Auditory distraction due to portable audio devices poses a hazard for pedestrians and cyclists. To explore solutions, auditory situation awareness (SA) was assessed within a simulated auditory roadway environment rendered via speakers. Participants' ability to report the presence and current/future location of vehicles was measured. The key manipulation was whether concurrently-presented distracting music was spatialised. Also manipulated were two common safety measures that impact spatialisation quality: whether bone or air conduction headphones were used, and whether sounds were presented in one or both ears. Spatialisation of distractors improved vehicle localisation in some conditions, as did presenting to one ear and via bone conduction. In Experiment 2, distractors were spatialised adaptively, to be diametrically opposed to targets. This intervention improved localisation without increasing workload. Results suggest that static or adaptive spatialisation should be considered as a safety measure for sound presentation in computing systems used by cyclists or pedestrians.

Relationship between the use of portable audio devices and taking notice of the approach informing sound of quiet vehicles

Lively discussion about the approach informing sound of quiet vehicles is being conducted; however, people often listen to media on portable audio devices in various environments and may not notice the approach informing sound. To clarify the relationship between the use of portable audio devices and the experience of encountering dangers associated with the approach of quiet vehicles, a questionnaire survey was conducted with 158 university students. Portable audio device ownership was 99.3%; only one respondent reported not owning such a device. Twenty-two respondents (15.5%) had encountered dangerous situations while using these devices outdoors. Thirteen respondents reported that they had experienced near-misses with vehicles while walking or biking, and seven reported that the vehicles were quiet vehicles. Multiple correspondence analysis revealed some differences in the usage habits of portable audio devices between the users who had and had not encountered dangerous situations. To improve notification effectiveness of quiet vehicles, usage habits related to portable audio devices, especially concerning young people, should be considered. In addition, means of preventing portable audio device users’ tendency to “tune out” other sounds should be addressed.

Flow control using audio tones in resonant microfluidic networks: towards cell-phone controlled lab-on-a-chip devices.

Fluid control remains a challenge in development of portable lab-on-a-chip devices. Here, we show that microfluidic networks driven by single-frequency audio tones create resonant oscillating flow that is predicted by equivalent electrical circuit models. We fabricated microfluidic devices with fluidic resistors (R), inductors (L), and capacitors (C) to create RLC networks with band-pass resonance in the audible frequency range available on portable audio devices. Microfluidic devices were fabricated from laser-cut adhesive plastic, and a "buzzer" was glued to a diaphragm (capacitor) to integrate the actuator on the device. The AC flowrate magnitude was measured by imaging oscillation of bead tracers to allow direct comparison to the RLC circuit model across the frequency range. We present a systematic build-up from single-channel systems to multi-channel (3-channel) networks, and show that RLC circuit models predict complex frequency-dependent interactions within multi-channel networks. Finally, we show that adding flow rectifying valves to the network creates pumps that can be driven by amplified and non-amplified audio tones from common audio devices (iPod and iPhone). This work shows that RLC circuit models predict resonant flow responses in multi-channel fluidic networks as a step towards microfluidic devices controlled by audio tones.

ポータブルオーディオ機器の発展

ポータブルオーディオ機器の発展

Low-Power and High-Efficiency Class-D Audio Amplifier Using Composite Interpolation Filter for Digital Modulators

This paper presents a high-efficiency digital class-D audio amplifier using a composite interpolation filter for portable audio devices. The proposed audio amplifier is composed of an interpolation filter, a delta-sigma modulator, and a class-D output stage. To reduce power consumption, the designed interpolation filter has an optimized composite structure that uses a direct-form symmetric and Lagrange FIR filters. Compared to the filters with homogeneous structures, the hardware cost and complexity are reduced by about half by the optimization. The coefficients of the digital deltasigma modulator are also optimized for low power consumption. The class-D output stage has gate driver circuits to reduce shoot-through current. The implemented class-D audio amplifier exhibited a high efficiency of 87.8 % with an output power of 57 mW at a load impedance of 16 6 and a power supply voltage of 1.8 V. An outstanding signal-to-noise ratio of 90 dB and a total harmonic distortion plus noise of 0.03 % are achieved for a single-tone input signal with a frequency of 1 kHz.

Spatial sound pick-up with a low number of microphones

Portable audio devices have become more and more popular during the last decade. Recent advances in audio compression and electronic miniaturization allow people to keep all their music and movies at hand, at all times. Nowadays people are using their smartphones everywhere as photo or video cameras. In order to provide a consumer possibility of 3D audio recording adapted to these kinds of devices, we developed a compact microphone array able to pick-up a full 3D sound scene, using less than four microphones. To compensate for the low number of microphones, which results in poor spatial selectivity, spatial post processing is applied to the microphone signals and improves the sound source localization. Another advantage is that the post processing makes the sound reproduction flexible. The 3D audio scene can be converted into any format to be rendered to any equipment and any device. The paper will describe various recording set-ups in combination with the associated post processing. As a first assessment, their performances in terms of sound localization accuracy will be compared using a new set of objective criteria descriptors.

Survey on the use of portable audio devices by university students

Survey on the use of portable audio devices by university students

Consumo musical: tensiones entre emisoras musicales juveniles y dispositivos portátiles

El artículo presenta los resultados de una investigación que tuvo como objetivo caracterizar las estrategias utilizadas por las emisoras musicales juveniles de Bogotá para mantener o aumentar el número de oyentes en el marco de las nuevas lógicas de consumo musical en dispositivos de audio portátiles. Se efectuaron entrevistas semiestructuradas a directores y programadores de cinco estaciones musicales de FM de la ciudad, con el fin de establecer las estrategias que ellos utilizan. Luego, se realizaron grupos focales con jóvenes de 14 a 17 y de 21 a 25 años, para determinar qué los lleva a sintonizar emisoras musicales cuando tienen acceso a la música que les gusta en estos dispositivos, como MP3 o iPod. La investigación estableció que la innovación en contenidos y la interacción con los oyentes a través de redes sociales son las principales estrategias para convocar a los oyentes. Estos sintonizan las emisoras porque presentan novedades informativas y temáticas, abren espacios de intercambio de opiniones vía redes y generan la sensación de cercanía y afinidad con los locutores.

Ear diseases among secondary school students in Xi'an, China: The role of portable audio device use, insomnia and academic stress

BackgroundHearing impairment negatively impacts students' development of academic, language and social skills. Even minimal unilateral hearing loss can hinder educational performance. We investigated the prevalence of ear diseases among secondary school students in the city of Xi'an, China in order to provide a foundation for evidence-based hearing healthcare.MethodsA stratified random sampling survey was conducted in 29 secondary schools. Demographics and medical histories were collected, and otologic examinations were performed. Questionnaires were administered to assess insomnia, academic stress and use of portable audio devices. Logistic regression analysis was used to identify factors associated with hearing impairment, and the association of sensorineural hearing loss with insomnia, academic stress and the use of portable audio devices was analyzed with the chi-square test.ResultsThe percentage of students with some form of ear disease was 3.32%. External ear disease, middle ear disease and sensorineural hearing loss occurred in 1.21%, 0.64% and 1.47% of the students, respectively. Boys had a relatively higher prevalence of ear disease than girls. According to our survey, the prevalence of sensorineural hearing loss increased significantly among the students with insomnia and extended use of portable audio devices, but not among those with elevated levels of academic stress. Hearing aids and surgical treatment were needed in 1.47% and 0.89% of the students, respectively.ConclusionsThere is a high prevalence of ear disease among secondary school students, and this should be given more attention. Insomnia and the excessive use of portable audio devices may be related to adolescent sensorineural hearing loss. It is important to establish and comply with an evidence-based preventive strategy.

Perceptibility of environmental sounds by earphone wearers listening to pop and rock music

To examine how the perceptibility of environmental sounds is affected by listening to music through earphones, the hearing thresholds for pure tones presented through a loudspeaker were measured. Under the condition that the listener wore canalphones, thresholds were considerably higher than those under the condition that the listener’s ears were open. When pseudo-music signals were presented through the canalphones at the A-weighted sound pressure level of 70 dB, the hearing threshold at 2 kHz was almost 70 dB higher than the absolute threshold. How environmental noise affects the listener’s comfortable level of music played on portable audio devices was also examined. The mean comfortable listening levels (A-weighted) under a quiet condition were between 65 dB and 69 dB and those under a noisy condition ranged between 73 dB and 76 dB. It was indicated that when listening to music through canalphones at a comfortable level on a busy street, many environmental sounds would be inaudible.

Podcasts by professional journals: online information and resources

As the popularity of portable audio devices such as the iPod increases, many periodicals are now supplementing their written format with recorded content by means of the medium of downloadable podcasts. This month’s Web words details some of the new ways that professionals can keep up to date with the news, views, information and research by looking at some of the more admired journals’ attempts at disseminating information via the web.

A Fully Integrated Variable-Gain Multi-tanh Low-Noise Amplifier for Tunable FM Radio Receiver Front-End

In this paper, we present a two-stage variable-gain low-noise amplifier (LNA) used in a frequency modulation (FM) radio receiver front-end for a variety of portable audio devices. We also describe a tunable antenna interface and a voltage regulator used in the front-end. The front-end can be tuned to resonate at FM frequencies from 63 to 129 MHz. The two-stage LNA achieves a programmable small-signal voltage gain from 0.5 to 32.5 dB in around 1-dB steps across the FM band from 76 to 108 MHz. Its input-referred noise voltage is less than 1.5 nV/radicHz in the high gain mode. Furthermore, the linearity of the LNA and front-end is improved by employing the multi-tanh design principle. In the low and high gain modes of the LNA, the measured IIP3 are -5.2 and -16.5 dBm, respectively, compared with -10.5 and -25.5 dBm without using the multi-tanh doublets. The whole LNA is fabricated in a TSMC 0.18-mum CMOS technology. It draws maximum 4.5 mA current (5.5 mA including the regulator) from a 1.35-V supply and occupies 0.15 mm2 of chip area. Experimental and simulation results are both provided to demonstrate the performance of the LNA and front-end.

A micropower low-distortion digital class-D amplifier based on an algorithmic pulsewidth modulator

A digital Class-D amplifier comprises a pulsewidth modulator (PWM) and an output stage. In this paper, we simplify the time-domain expression for the algorithmic PWM linear interpolation (LI) sampling process and analytically derive its double Fourier series expression. By means of our derivation, we show that the nonlinearities of the LI process are very low, especially given its modest computation complexity and low sampling frequency. In particular, the total-harmonic distortion (THD) /spl ap/0.02% and foldback distortion is -98.4 dB (averaged from modulation indexes M=0.1 to 0.9) for the 4-kHz voiceband bandwidth @1-kHz input, 48-kHz sampling. We also describe a simple hardware for realizing the LI process. We propose a frequency doubler (with small overheads) for the pulse generator for the PWM, thereby reducing the counter clock rate by 2, leading to a substantial /spl sim/47% power dissipation reduction for the Class-D amplifier. By means of computer simulations and on the basis of experimental measurements, we verify our double Fourier series derivation and show the attractive attributes of a Class-D amplifier embodying our simplified LI sampling expression and reduced clock rate pulse generator. We show that our Class-D amplifier design is micropower (/spl sim/60 /spl mu/W @1.1 V and 48-kHz sampling rate, and THD /spl ap/0.03%) and is suitable for practical power-critical portable audio devices, including digital hearing aids.

Analog implementation of an active noise controller system for portable audio applications

The active noise controller (ANC) system described here implements a practical design that significantly decreases background noise of signals common to most portable audio devices. This is achieved by a mixture of conventional ANC blocks with less traditional implementations, including a combined FIR/IIR structure using switched-capacitor blocks such as summers, integrators, multipliers, and delays. The proposed design also works as a stand-alone system and it has been successfully implemented on a 1.2-/spl mu/m CMOS technology.

Virtual bass for home entertainment, multimedia PC, game station and portable audio systems

In digital audio playback systems for home entertainment, multimedia PC, game station and portable audio devices, there is a strong demand to produce deep bass using small multimedia speakers and earphones, without the need for additional subwoofer or expensive speakers/earphones. This paper describes a technique in synthesizing psycho-acoustic bass over a pair of stereo speakers using the pitch perception theory. This new method of creating a bass effect for the musical signal has been found to be very effective and simple in implementation, without increasing significant cost in many modern digital audio systems. A subjective evaluation is also being performed to validate the virtual bass implementation.