Query: what is condenser microphone

Candidate papers:

abstract: On a bright fall morning last October there was a historic meeting among three industry stalwarts that was of particular interest to the acoustics community. Gerhard Sessler and James West returned to New Jersey, the home state of Bell Labs where they both started their professional careers, to be inducted into the "New Jersey Inventors' Hall of Fame." Ray Stata, founder of Analog Devices and a pioneer of Micro Elecro MechanicalSystems (MEMS) devices, was passing through on business. The three got together at the beautiful Reeves Reed arboretum in Summit, New Jersey for a discussion on the evolution of consumer microphones towards MEMS (see Fig.1) Drs. Sessler and West invented the Electret Condenser Microphone (ECM) at Bell Labs in the early 1960's. The low cost and small size of the ECM has enabled the production of modern consumer devices such as cell phones, headsets, and video cameras. As a result, in excess of 2 billion ECM microphones shipped in 2008. In 1965, Ray Stata founded Analog Devices, a world leader in semiconductor converter and amplifier microchips today. In the early 1990's Ray Stata played a key role in evangelizing MEMS technology, enabling the manufacture of small, low cost accelerometers and gyroscopes for automotive and consumer markets. More recently, he, with his company, developed world leading MEMS microphone technology. In the 1980's Dr. Sessler did much of the early academic research in MEMS microphones at the University of Darmstadt, Germany. Dr. Sessler is recognized as one of the earliest advocates for research in the field of silicon microphones. Amid the beauty of the autumnal foliage of the Reeves Reed Arboretum, Sessler, West, and Stata sat down to discuss the evolution of microphones and consider what the future might hold.
author_names: Gary W Elko

K P Harney
title: A History of Consumer Microphones: The Electret Condenser Microphone Meets Micro Electro Mechanical Systems
year: 2009

abstract: I 've been interested in microphones for some time, especially those used to record music in concert and studio settings. More recently, however, I've become especially interested in how various microphones differ, how to measure and compare those differences, and what design trade offs go into the development of a new microphone. This article examines a particular kind of microphone, the acoustic dipole or "gradient" microphone and its design parameters1. First I'll describe its operation mathematically in enough detail to predict frequency and polar response characteristics in a spreadsheet. Next, I'll discuss the techniques needed to obtain accurate measurements of microphone frequency and polar response, using a computer sound card and some simple software programs. The spreadsheet and computer source code are posted online (www.audioXpress.com) for readers to download. Finally, I'll show the construction of a prototype dipole microphone using two omnidirectional electret condenser microphone cartridges. My goal here is not to produce a design that's better or different from existing designs, but rather to gain a more complete understanding of what goes into microphone design and measurement. This way, we can all be a little more confident about making the best use of the microphones that are available to us.
author_names: Mark S Williamsen
title: Design and Measurement Of a Dipole Microphone
year: 2009

abstract: Background noise studies have been extended from air condenser microphones to piezoresistive, electret condenser, and ceramic microphones. Theoretical models of the respective noise sources within each microphone are developed and are used to derive analytical expressions for the noise power spectral density for each type. Several additional noise sources for the piezoresistive and electret microphones, beyond what had previously been considered, were applied to the models and were found to contribute significantly to the total noise power spectral density. Experimental background noise measurements were taken using an upgraded acoustic isolation vessel and data acquisition system, and the results were compared to the theoretically obtained expressions. The models were found to yield power spectral densities consistent with the experimental results. The measurements reveal that the 1/f noise coefficient is strongly correlated with the diaphragm damping resistance, irrespective of the detection technology, i.e. air condenser, piezoresistive, etc. This conclusion has profound implications upon the expected 1/f noise component of micromachined (MEMS) microphones.
author_names: Allan J Zuckerwar

Theodore R Kuhn

Roman Serbyn
title: Background noise in piezoresistive, electret condenser, and ceramic microphones.
venue: The Journal of the Acoustical Society of America
year: 2003

abstract: Acoustics represents a body of science that is rich in theory and new concepts and has many applications in everyday life. Unfortunately, many undergraduates are not afforded the opportunity to explore acoustics past a brief introduction. The purpose of this project, then, is to implement an acoustics experiment in the undergraduate advanced laboratory course in the CWRU Physics Department. The experiment will closely follow suggestions made by Robertson and Parker in their 2012 paper Acoustic impulse response method as a source of undergraduate research projects and advanced laboratory experiments. Students will learn skills in signal processing and data analysis as they probe the acoustic impulse responses of PVC waveguides with a condenser microphone and wide range monitor. Introduction Acoustics represents a body of science that is rich in theory and new concepts and has many direct applications in everyday life. Since acoustics is the study of sound, any noise in the world can provide meaningful insight in some way, from an orchestra concert to radio static and the silence of an anechoic chamber to the sonic boom of a passing jet. Sound is a wave, so concepts like interference, refraction and so on show up almost everywhere. Furthermore, following wave mechanics in general, many acoustic phenomena have optical analogues. For example, single slit diffraction, double slit interference and Lloyd's mirror experiment. Students can complete an acoustics experiment and learn some of the same concepts that they would learn completing an optics experiment, which may be more expensive and delicate. Laboratory experiments and courses in acoustics have already been implemented at other universities. Kettering University in Flint, MI runs a complete laboratory course in acoustics. The course is designed to impart a select few concepts in acoustics while coupling with the university's cooperative program to teach real world engineering skills. The U.S. Naval Academy in Annapolis, MD utilizes ultrasound transducers in one demonstration to teach about multiple source interference and its application to beamforming. Middle Tennessee State University in Murfreesboro, TN suggests an impulse response experiment that uses polyvinyl chloride (PVC) pipes as waveguides. These last two examples are particularly useful because the experimental equipment is simple, robust, and is of good enough quality to provide useful results. Following one of these experiments in an undergraduate laboratory course would be a simple investment to get started in acoustics. The purpose of this project, then, is to implement an acoustics experiment in the undergraduate advanced laboratory course in the Case Western Reserve University (CWRU) Physics Department. In their paper "Acoustic impulse response method as a source of undergraduate research projects and advanced laboratory experiments" Robertson and Parker describe an acoustics experiment for an advanced undergraduate laboratory course. Using a simple setup consisting of a speaker, microphone, computer and data acquisition module, they measure the acoustic impulse response of various PVC waveguides. The experiment in this project will follow their design very closely to produce a useful learning opportunity for physics students at CWRU. The experiment will expose students to interesting acoustics concepts such as propagation in waveguides, filter response characteristics, and signal processing. Introducing this experiment to the laboratory course will provide new horizons for students to explore. Theory LTI Systems The theoretical basis of this project is derived from linear time invariant (LTI) systems theory. Any signals and systems text (see, for example, Ref. [4] is sufficient for explaining the level of theory presented in this paper. This project assumes that all of the systems explored by the experiment described here are LTI systems. Assuming linearity and time invariance makes the math and analysis required to complete the experiment much more tractable for undergraduates. The first major assumption about LTI systems is that they are linear. That is to say, the output of the system is linearly related to the input. For a larger input, the system yields a proportionally larger output. An important result of linearity is linear wave superposition, which is a familiar concept to a majority students in the advanced undergraduate physics laboratory class at CWRU, who will have completed the introductory physics courses that first present this concept. Linear wave superposition states that when two signals are present in a medium, the resultant signal at any point in the medium is equal to the sum of the two original signals at that same point, independent of the value of any of the signals anywhere else. When applied to systems, linearity yields equation (1) below, which illustrates linearity and wave superposition mathematically. In equation (1) x1(t) and x2(t) are inputs to the system, multiplied by constant gains of a1 and a2, respectively. The arrow represents the inputs x1(t) and x2(t) passing through the system and yielding outputs y1(t) and y2(t) respectively. x (t) a x (t) y (t) a y (t) a1 1 2 2 a1 1 2 2 (1) The second assumption about LTI systems is that they are time independent. That is to say, the output of the system is temporally related to the input. For a delayed input, the system yields a similarly delayed output. For a given input, whether it is input to the system in the morning at 0500 or late at night at 2200, an LTI system will always give the same output, delayed relative to the input the same amount each time. Equation (2) below illustrates time invariance, where x(t T) is an input, x(t) delayed in time by T, and y(t T) is the output corresponding to input x(t) delayed in time by T. (t (t x T y T (2) An interesting result comes from these two assumptions of linearity and time invariance: an LTI system can be completely described by its impulse response. A system's impulse response is exactly what it sounds like: it is the response, or output, of the system for an input impulse. With a system's impulse response, h(t) and the convolution operation, equation (3) shows how the system's output, y(t) can be calculated for any arbitrary input, x(t) Equation (4) shows how the convolution operation is carried out. (t) x(t) (t) y h (3) (t) (t)h(t )dt y
author_names: Michael Anderson

Jesse Berezovsky
title: Advanced Undergraduate Acoustics Experiment
year: 2014

abstract: So what's a field recorder? Here's my definition: a device that lets you make a recording in a field. As in: no electricity, no roads, no buildings, no shelter, no access to any gear that you cannot carry on your back. That means a field recorder should be small, lightweight, and rugged. It should have either a built in microphone or decent microphone preamps; ideally it will have both. Phantom power (for driving condenser mics) is a plus, as are line inputs.
author_names: Mark Nelson
title: Outstanding in the field
venue: Volume 38, Number 5, October 2011
year: 2019

abstract: Acoustic diagnosis system with condenser microphone has some attractive characters what is more cheaper for cost of devices of sensor, is not keeping contact with machinery components and is wide band range on frequency compared with piezoelectric accelerometers. This paper proposes a method to do condition diagnosis about strong non stationary signal generated by operating rotating machineries which are rolling bearings. Especially, a signal processing technique in order to eliminate non stationary noises including operating sound is described by adopting locally stationary AR model a kind of system identification. Further, the optimum order of locally stationary AR model is determined from presumption of division terms. The effectiveness of this method has been identified by experiment based on a rotary simulator device on rolling bearings.
author_names: Hiromitsu Ohta

Kunisato Seto
title: Acoustic Diagnosis on Rolling Bearings Based on Presumption of a Division Term by Locally Stationary AR Model
year: 2004

abstract: Recording and analysis of vocalizations The vocalizations of each bird were recorded using a small condenser microphone that was located in each sound attenuating chamber. Beginning at approximately 30 days after tutoring, recordings were made frequently, with intervals not exceeding 9 days. These signals were digitized, displayed as spectrograms in real time and stored as computer files (Avisoft Recorder) Across renditions, the crystallized songs of birds often varied in length, with the last phrase sometimes not included. Spectrograms of crystallized songs that are displayed in this paper were chosen to show all of the phrase types of typical length found in these songs. Songs were scored with regard to whether adjacent phrases were placed in correct versus incorrect relative position; these values were then evaluated with respect to what would be expected by chance.
author_names: Rustem Khazipov

Anton M Sirota

Xavier Leinekugel

Gregory L Holmes

Yehezkel Ben-Ari

Gyorgy Buzsaki
title: autopsy; five of the birds in the reversed phrase order group and seven in the forward phrase order group were confirmed to be males.
year: 2004

abstract: In designing a controller, one way to avoid an energy spillover is to use what is called the zero spillover scheme. However, practical limitations may make such a controller impossible to realize, and one will need to implement a relaxed version of this controller called a relaxed zero spillover controller (RZSC) Here, analytical and experimental investigations into a RZSC scheme are presented. This controller has been used for active structural acoustic control (ASAC) of sound transmission into an enclosure. Noise is transmitted through the flexible boundary of the enclosure, and piezoceramic patches, mounted on the flexible boundary, are used as actuators. Polyvinylidene fluoride sensors are used on the flexible boundary and condenser microphone sensors are used inside and outside the enclosure. The stability of the chosen RZSC scheme for a single input, single output system and the extension to multiple input, multiple output systems are discussed along with other issues.
author_names: M Al-Bassyiouni

Balakumar Balachandran
title: Relaxed zero spillover controller for active structural acoustic control systems
venue: SPIE Smart Structures and Materials Nondestructive Evaluation and Health Monitoring
year: 2003

abstract: Although the speed of sound in air was measured with reasonable accuracy about the middle of the 17th century, intensity measurements did not properly begin until Rayleigh, in 1882, published his experiments with what came to be called the Rayleigh disc. The accuracy remained relatively low (about 10% until about 1940. In the meantime the working standard for measurements in acoustics had come to be the condenser microphone which is a reciprocal transducer. By using the reciprocity method its calibration has improved by about two orders of magnitude, being now carried out to a precision of about 10 3. This is quite adequate for most purely physical measurements and more than adequate for many others such as sound absorption coefficients of surfaces or sound transmission loss of partitions. In most measurements of a psychoacoustical nature (threshold of hearing, loudness, etc. or even where a human subject is involved in only a passive role, the errors of measurement are still very great being of the order of 10 1 or often greater.
author_names: George J Thiessen
title: Progress in Measurements in Acoustics
year: 1967

abstract: Abstract The purpose of the study was to determine what changes three types of microphones undergo during compression and decompression to 19 ATA (equiv. to 600 feet of sea water) using a mixture of helium and oxygen. A reciprocity calibrated ceramic microphone was used as the standard for observing the changes of a cardioid (ribbon) type condenser microphone. The results indicate that sensitivity of all microphones decreases as ambient pressure increases. In addition, there are substantial changes in the linearity of the transducers especially at frequencies above 3000 Hertz. The ceramic microphone demonstrated the most consistent responses during descent and ascent. At 17 hours post dive, it also showed a frequency response that was within one dB of the pre dive values at all frequencies tested. From this investigation, it would appear that none of the three types of microphones is ideally suited for speech communication in helium oxygen environments due to the roll off in sensitivity at the high frequencies at depths greater than 200 feet.
author_names: Thomas Murry

Russell L Sergeant
title: Response Variations of Three Types of Microphones Pressurized to 19 ATA
year: 1971