Microphone Interface Research Articles

The Evolution of Integrated Interfaces for MEMS Microphones.

Over the last decade, MEMS microphones have become the leading solution for implementing the audio module in most portable devices. One of the main drivers for the success of the MEMS microphone has been the continuous improvement of the corresponding integrated interface circuit performance in terms of both dynamic range and power consumption, which enabled the introduction in mobile devices of additional functionalities, such as Hi-Fi audio recording or voice commands. As a result, MEMS microphone interface circuits evolved from just simple amplification stages to complex mixed-signal circuits, including A/D converters, with ever improving performance. This paper provides an overview of such evolution based on actual design examples, focusing, finally, on the latest cutting-edge solutions.

Response Time to Stimuli in Division I Soccer Players

The purpose of this investigation was to examine the effect of auditory stimuli (AS) and visual stimuli (VS) on sprint time, sprint speed, and reaction time in National Collegiate Athletic Association Division I male soccer players. Fifteen healthy subjects (mean age 22.1 ± 1.6 years) volunteered for the study. This experiment was conducted on a regulation soccer field, using a wireless timing system. Subjects stood on a touch-and-release pad and were instructed a prompt (AS: "go" command via a microphone interface, VS: movement of a player located 10 m from the start) to run 20 m through the finish line timing gates without decelerating. After 3 submaximal sprint trials at 50%, conditions (AS and VS) were randomized and performed 3 times by each subject. The best sprint time, sprint speed, and reaction time were recorded. Paired t-tests were conducted on dependent variables to determine statistically significant differences. An alpha level was set at p ≤ 0.05. Sprint time was reduced in response to VS as compared to AS (3.76 ± 0.16 seconds vs. 3.85 ± 0.15 seconds, p = 0.001). Sprint speed (distance covered) was greater in VS compared to AS (5.3 ± 0.21 m · s vs. 5.1 ± 0.19 m · s, p < 0.001), and reaction time was reduced in VS compared to AS (0.53 ± 0.048 seconds vs. 0.61 ± 0.044 seconds, p = 0.001). These data show that VS rather than AS improve sprint response times in collegiate male soccer athletes. The data suggest that performance on the field may be improved if coaches and players strategize to integrate visual cues (e.g., gestures and signals) during practices and games.

Reproducing works of Calder

Many fine art pieces have been reproduced in digital form. The digital reproductions have been used to store and transmit the original work. In contrast, mobiles, or moving sculptures, such as those designed by Alexander Calder cannot be reproduced realistically by photographs and/or static images. The real characteristics of mobiles come from the motions generated by interactive external forces applied to their structures. Hence people could not fully enjoy them through static images or even static three-dimensional models. We present a virtual mobile system where users can easily control the mobile and can feel the impressions that the artist originally intended to provide. Virtual winds are generated by blowing on a microphone which then exert external forces to the mobile. This microphone interface lets users control the mobile while they are watching it through a monitor. We introduce a linear time solution for the constraint dynamics and an improved impulse dynamics to speed up the simulation. Using these techniques, we achieve a real-time simulation of the mobile on personal computers. The techniques presented can easily be extended to simulate other interactive dynamics systems. Copyright ©2001 John Wiley & Sons, Ltd.

Reproducing works of Calder

AbstractMany fine art pieces have been reproduced in digital form. The digital reproductions have been used to store and transmit the original work. In contrast, mobiles, or moving sculptures, such as those designed by Alexander Calder cannot be reproduced realistically by photographs and/or static images. The real characteristics of mobiles come from the motions generated by interactive external forces applied to their structures. Hence people could not fully enjoy them through static images or even static three‐dimensional models. We present a virtual mobile system where users can easily control the mobile and can feel the impressions that the artist originally intended to provide. Virtual winds are generated by blowing on a microphone which then exert external forces to the mobile. This microphone interface lets users control the mobile while they are watching it through a monitor. We introduce a linear time solution for the constraint dynamics and an improved impulse dynamics to speed up the simulation. Using these techniques, we achieve a real‐time simulation of the mobile on personal computers. The techniques presented can easily be extended to simulate other interactive dynamics systems. Copyright ©2001 John Wiley &amp; Sons, Ltd.

Measurement of Respiratory Acoustic Signals

The use of electret microphones to measure lung sounds is widespread because of their small size, high fidelity, and low cost. Typically, an air cavity is placed between the skin surface and the microphone to convert the chest wall vibrations into a measurable sound pressure. The importance of air cavity depth on this transduction process was investigated in this study. An acoustic model of chest wall--air cavity--microphone interface was developed and the predicted effects of depth were compared with measurements performed using an artificial chest wall and lung sounds from a healthy subject. Model predictions are in general agreement with both in vitro and in situ measurements and indicate that the overall high-frequency response of the transduction diminishes with increasing cavity depth. This finding suggests that smaller cavity depths are more appropriate for detection of lung sounds over a wide band width and stresses the importance of coupler size on microphone measurements.