DOCSLIB.ORG

The Microphone Handbook.Pdf

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
The Microphone Handbook.Pdf Earg_FM.qxd 15/9/04 4:54 PM Page i THE MICROPHONE BOOK Second edition Earg_FM.qxd 14/9/04 3:11 PM Page ii Earg_FM.qxd 14/9/04 3:11 PM Page iii THE MICROPHONE BOOK Second edition John Eargle AMSTERDAM • BOSTON • HEIDELBERG • LONDON • NEW YORK • OXFORD PARIS • SAN DIEGO • SAN FRANCISCO • SINGAPORE • SYDNEY • TOKYO Focal Press is an imprint of Elsevier Earg_FM.qxd 14/9/04 3:11 PM Page iv Focal Press An imprint of Elsevier Linacre House, Jordan Hill, Oxford OX2 8DP 30 Corporate Drive, Burlington MA 01803 First published 2005 Copyright © 2005, John Eargle. All rights reserved The right of John Eargle to be identified as the author of this work has been asserted in accordance with the Copyright, Designs and Patents Act 1988 No part of this publication may be reproduced in any material form (including photocopying or storing in any medium by electronic means and whether or not transiently or incidentally to some other use of this publication) without the written permission of the copyright holder except in accordance with the provisions of the Copyright, Designs and Patents Act 1988 or under the terms of a licence issued by the Copyright Licensing Agency Ltd, 90 Tottenham Court Road, London, England W1T 4LP. Applications for the copyright holder’s written permission to reproduce any part of this publication should be addressed to the publisher Permissions may be sought directly from Elsevier’s Science and Technology Rights Department in Oxford, UK: phone: (+44) (0) 1865 843830; fax: (+44) (0) 1865 853333; e-mail: [email protected]. You may also complete your request on-line via the Elsevier homepage (www.elsevier.com), by selecting ‘Customer Support’ and then ‘Obtaining Permissions’ British Library Cataloguing in Publication Data A catalogue record for this book is available from the British Library Library of Congress Cataloguing in Publication Data A catalogue record for this book is available from the Library of Congress ISBN 02405 1961 2 For information on all Focal Press publications visit our website at: www.focalpress.com Typeset by Newgen Imaging Systems (P) Ltd, Chennai, India Printed and bound in the United States Working together to grow libraries in developing countries www.elsevier.com | www.bookaid.org | www.sabre.org Earg_FM.qxd 15/9/04 4:55 PM Page v CONTENTS Preface to the First Edition vii Preface to the Second Edition ix Symbols Used in This Book x 1 A Short History of the Microphone 1 2 Basic Sound Transmission and Operational Forces on Microphones 7 3 The Pressure Microphone 22 4 The Pressure Gradient Microphone 50 5 First-Order Directional Microphones 66 6 High Directionality Microphones 91 7 Microphone Measurements, Standards, and Specifications 105 8 Electrical Considerations and Electronic Interface 117 9 Overview of Wireless Microphone Technology 142 10 Microphone Accessories 152 11 Basic Stereophonic Recording Techniques 166 12 Stereo Microphones 184 13 Classical Stereo Recording Techniques and Practice 194 14 Studio Recording Techniques 217 15 Surround Sound Microphone Technology 243 16 Surround Recording Case Studies 271 Earg_FM.qxd 14/9/04 3:11 PM Page vi vi Contents 17 A Survey of Microphones in Broadcast and Communications 290 18 Fundamentals of Speech and Music Reinforcement 301 19 Overview of Microphone Arrays and Adaptive Systems 322 20 Care and Maintenance of Microphones 334 21 Classic Microphones: The Author’s View 338 References and Bibliography 367 Index 373 Earg_FM.qxd 14/9/04 3:11 PM Page vii PREFACE TO THE FIRST EDITION Most sound engineers will agree that the microphone is the most important element in any audio chain, and certainly the dazzling array of current models, including many that are half-a-century old, attests to that fact. My love affair with the microphone began when I was in my teens and got my hands on a home-type disc recorder. Its crystal micro- phone was primitive, but I was nonetheless hooked. The sound bug had bitten me, and, years of music schooling not withstanding, it was inevitable that I would one day end up a recording engineer. About thirty years ago I began teaching recording technology at vari- ous summer educational programs, notably those at the Eastman School of Music and later at the Aspen Music Festival and Peabody Conservatory. I made an effort at that time to learn the fundamentals of microphone per- formance and basic design parameters, and my Microphone Handbook, published in 1981, was a big step forward in producing a text for some of the earliest collegiate programs in recording technology. This new book from Focal Press presents the technology in greater depth and detail and, equally important, expands on contemporary usage and applications. The Microphone Book is organized so that both advanced students in engineering and design and young people targeting a career in audio can learn from it. Chapter 1 presents a short history of the microphone. While Chapters 2 through 6 present some mathematically intensive material, their clear graphics will be understandable to those with little technical background. Chapters 7 through 10 deal with practical matters such as standards, the microphone-studio electronic interface, and all types of accessories. Chapters 11 through 17 cover the major applications areas, with emphasis on the creative aspects of music recording in stereo and sur- round sound, broadcast/communications, and speech/music reinforce- ment. Chapter 18 presents an overview of advanced development in microphone arrays, and Chapter 19 presents helpful hints on microphone maintenance and checkout. The book ends with a comprehensive micro- phone bibliography and index. Earg_FM.qxd 14/9/04 3:11 PM Page viii viii Preface to the First Edition I owe much to Leo Beranek’s masterful 1954 Acoustics text, A. E. Robertson’s little known work, Microphones, which was written for the BBC in 1951, as well as the American Institute of Physics’ Handbook of Condenser Microphones. As always, Harry Olson’s books came to my aid with their encyclopedic coverage of everything audio. Beyond these four major sources, any writer on microphones must rely on technical journals and on-going discussions with both users and manufacturers in the field. I would like to single out for special thanks the following persons for their extended technical dialogue: Norbert Sobol (AKG Acoustics), Jörg Wuttke (Schoeps GmbH), David Josephson (Josephson Engineering), Keishi Imanaga (Sanken Microphones), and in earlier days Steve Temmer and Hugh Allen of Gotham Audio. Numerous manufacturers have given permission for the use of photographs and drawings, and they are credited with each usage in the book. John Eargle April 2001 Earg_FM.qxd 14/9/04 3:11 PM Page ix PREFACE TO THE SECOND EDITION The second edition of The Microphone Book follows the same broad subject outline as the first edition. Most of the fundamental chapters have been updated to reflect new models and electronic technology, while those chapters dealing with applications have been significantly broadened in their coverage. The rapid growth of surround sound technology merits a new chap- ter of its own, dealing not only with traditional techniques but also with late developments in virtual imaging and the creation of imaging that conveys parallax in the holographic sense. Likewise, the chapter on microphone arrays has been expanded to include discussions of adaptive systems as they involve communications and useful data reduction in music applications. Finally, at the suggestion of many, a chapter on classic microphones has been included. Gathering information on nearly thirty models was a far more difficult task than one would ever have thought, and it was truly a labor of love. John Eargle Los Angeles, June 2004 Earg_FM.qxd 14/9/04 3:11 PM Page x SYMBOLS USED IN THIS BOOK a radius of diaphragm (mm); acceleration (m/s2) A ampere (unit of electrical current) AF audio frequency c speed of sound (334 m/s at normal temperature) ЊC temperature (degrees celsius) d distance (m) dB relative level (decibel) dB(A) A-weighted sound pressure level dBu signal voltage level (re 0.775 volt rms) DC critical distance (m) DI directivity index (dB) E voltage (volt dc) e(t) signal voltage (volt rms) f frequency in hertz (s–1) HF high frequency Hz frequency (hertz, cycles per second) I acoustical intensity (W/m2) I dc electrical current, ampere (Q/s) i(t) signal current (ampere rms) ϫ 2 I0 mechanical moment of inertia (kg m ) j complex algebraic operator, equal to ͙ Ϫ 1 k wave number (2␲/␭) kg mass, kilogram (SI base unit) ЊK temperature (degrees kelvin, SI base unit) LF low frequency ␮ LP sound pressure level (dB re 20 Pa) ␮ LR reverberant sound pressure level (dB re 20 Pa) ␮ LN noise sound pressure level (dB re 20 Pa) m meter (SI base unit) MF mid frequency mm millimeter (m ϫ 10–3) ␮m micrometer or micron (m ϫ 10–6) Earg_FM.qxd 14/9/04 3:11 PM Page xi Symbols Used in This Book xi M microphone system sensitivity, mV/Pa MD capacitor microphone base diaphragm sensitivity, V/Pa N force, newton (kg, m/s2) p; p(t) rms sound pressure (N/m2) P power (watt) Q electrical charge (coulombs, SI base unit) Q directivity factor r distance from sound source (m) R, ⍀ electrical resistance (ohm) R room constant (m3 or ft3) RE random efficiency of microphone (also REE) RF radio frequency RH relative humidity (%) s second (SI base unit) S surface area (m2) T torque (N ϫ m) T, t time (s) T magnetic flux density (tesla) T60 reverberation time (seconds) T0 diaphragm tension (newton/meter) torr atmospheric pressure; equal to mm of mercury (mmHg), or 133.322 Pa
Load more

Recommended publications
  • Tools for Digital Audio Recording in Qualitative Research
    Sociology at Surrey University of Surrey social researchUPDATE • The technology needed to make digital recordings of interviews and meetings for the purpose of qualitative research is described. • The advantages of using digital audio technology are outlined. • The technical background needed to make an informed choice of technology is summarised. • The Update concludes with brief evaluations of the types of audio recorder currently available. Tools for Digital Audio Recording in Qualitative Research Alan Stockdale In a recent book Michael Patton writes, “As a naïveté, can heighten the sense of “being Dr. Stockdaleʼs training is in good hammer is essential to fine carpentry, there”. For discussion of the naturalization cultural anthropology. He is a a good tape recorder is indispensable to of audio recordings in qualitative research, senior research associate at fine fieldwork” (Patton 2002: 380). He see Ashmore and Reed (2000). Education Development Center goes on to cite an example of transcribers in Boston, Massachusetts, at one university who estimated that 20% Why digital? of the tapes given to them “were so badly where he currently serves Audio Quality as an investigator on several recorded as to be impossible to transcribe The recording process used to make genetics education research accurately – or at all.” Surprisingly there analogue recordings using cassette tape is remarkably little discussion of tools and introduces noise, particularly tape hiss. projects funded by the U.S. techniques for recording interviews in the Noise can drown out softly spoken words National Institutes of Health. qualitative research literature (but see, for and makes transcription of normal speech example, Modaff and Modaff 2000).
    [Show full text]
  • How to Tape-Record Primate Vocalisations Version June 2001
    How To Tape-Record Primate Vocalisations Version June 2001 Thomas Geissmann Institute of Zoology, Tierärztliche Hochschule Hannover, D-30559 Hannover, Germany E-mail: [email protected] Key Words: Sound, vocalisation, song, call, tape-recorder, microphone Clarence R. Carpenter at Doi Dao (north of Chiengmai, Thailand) in 1937, with the parabolic reflector which was used for making the first sound- recordings of wild gibbons (from Carpenter, 1940, p. 26). Introduction Ornithologists have been exploring the possibilities and the methodology of tape- recording and archiving animal sounds for many decades. Primatologists, however, have only recently become aware that tape-recordings of primate sound may be just as valuable as traditional scientific specimens such as skins or skeletons, and should be preserved for posterity. Audio recordings should be fully documented, archived and curated to ensure proper care and accessibility. As natural populations disappear, sound archives will become increasingly important. This is an introductory text on how to tape-record primate vocalisations. It provides some information on the advantages and disadvantages of various types of equipment, and gives some tips for better recordings of primate vocalizations, both in the field and in the zoo. Ornithologists studying bird sound have to deal with very similar problems, and their introductory texts are recommended for further study (e.g. Budney & Grotke 1997; © Thomas Geissmann Geissmann: How to Tape-Record Primate Vocalisations 2 Kroodsman et al. 1996). For further information see also the websites listed at the end of this article. As a rule, prices for sound equipment go up over the years. Prices for equipment discussed below are in US$ and should only be used as very rough estimates.
    [Show full text]
  • USB Recording Microphone
    FEATURES USING YOUR MICROPHONE Adjusting your microphone’s angle Front Position yourself 1.5 ft. (0.46 m) in front of the microphone with the Insignia Loosen the adjustment knobs to move the microphone to the position you Microphone: want, then retighten the knobs to secure. Captures audio. logo and mute button facing you. Mute button/Status LED: QUICK SETUP GUIDE Lights blue when connected to power. Lights red when muted. Adjustment knob USB Recording 1.5 ft. (0.46 m) Micro USB port: Tilt adjustment knobs: Attaching to a microphone stand Microphone Connect your USB cable (included) Adjust your microphone’s tilt angle. Your microphone’s cardioid recording pattern captures audio primarily from the 1 Unscrew the desk stand’s adjustment knob to remove the microphone. from this port to your computer. front of the microphone. This is ideal for recording podcasts, livestreams, NS-CBM19 Desk stand: voiceovers, or a single instrument or voice. Desk stand Holds your microphone. adjustment knob PACKAGE CONTENTS Side • Microphone • Desk stand Microphone 2 Screw the microphone onto a stand that has a 1/4" threaded adapter. • USB cable • Quick Setup Guide Desk stand adjustment knob Mounting hole: SYSTEM REQUIREMENTS Attaches the microphone Remove the desktop stand to screw Cardioid Windows 10®, Windows 8®, Windows 7®, or Mac OS X 10.4.11 or later to the stand. onto any ¼" threaded stand. recording pattern Mounting hole Before using your new product, please read these instructions to prevent any damage. SETTING UP YOUR MICROPHONE SETTING THE VOLUME The microphone is picking up background noise determined by turning the equipment off and on, the user is encouraged to try to correct the interference by Connecting to your computer Use your computer’s system settings or recording software to adjust the • This cardioid microphone picks up audio from the front and minimizes noise one or more of the following measures: Connect the USB cable (included) from your microphone to your computer.
    [Show full text]
  • Introduction to Electrets: Principles, Equations, Experimental Techniques
    Introduction to electrets: Principles, equations, experimental techniques Gerhard M. Sessler Darmstadt University of Technology Institute for Telecommunications Merckstrasse 25, 64283 Darmstadt, Germany [email protected] Darmstadt University of Technology • Institute for Telecommunications Overview Principles Charges Materials Electret classes Equations Fields Forces Currents Charge transport Experimental techniques Charging Surface potential Thermally-stimulated discharge Dielectric measurements Charge distribution (surface) Charge distribution (volume) Darmstadt University of Technology • Institute for Telecommunications Electret charges Darmstadt University of Technology • Institute for Telecommunications Energy diagram and density of states for a polymer Darmstadt University of Technology • Institute for Telecommunications Electret materials Polymers Anorganic materials Fluoropolymers (PTFE, FEP) Silicon oxide (SiO 2) Polyethylene (HDPE, LDPE, XLPE) Silicon nitride (Si 3N4) Polypropylene (PP) Aluminum oxide (Al 2O3) Polyethylene terephtalate (PET) Glas (SiO 2 + Na, S, Se, B, ...) Polyimid (PI) Photorefractive materials Polymethylmethacrylate (PMMA) • Polyvinylidenefluoride (PVDF) • Ethylene vinyl acetate (EVA) • • • Cellular and porous polymers Cellular PP Porous PTFE Darmstadt University of Technology • Institute for Telecommunications Charged or polarized dielectrics Category Materials Charge or polarization Properties Applications Density Geometry [mC/m2 ] Real-charge External electric FEP, SiO electrets 2 0.1 - 1 field
    [Show full text]
  • Army Radio Communication in the Great War Keith R Thrower, OBE
    Army radio communication in the Great War Keith R Thrower, OBE Introduction Prior to the outbreak of WW1 in August 1914 many of the techniques to be used in later years for radio communications had already been invented, although most were still at an early stage of practical application. Radio transmitters at that time were predominantly using spark discharge from a high voltage induction coil, which created a series of damped oscillations in an associated tuned circuit at the rate of the spark discharge. The transmitted signal was noisy and rich in harmonics and spread widely over the radio spectrum. The ideal transmission was a continuous wave (CW) and there were three methods for producing this: 1. From an HF alternator, the practical design of which was made by the US General Electric engineer Ernst Alexanderson, initially based on a specification by Reginald Fessenden. These alternators were primarily intended for high-power, long-wave transmission and not suitable for use on the battlefield. 2. Arc generator, the practical form of which was invented by Valdemar Poulsen in 1902. Again the transmitters were high power and not suitable for battlefield use. 3. Valve oscillator, which was invented by the German engineer, Alexander Meissner, and patented in April 1913. Several important circuits using valves had been produced by 1914. These include: (a) the heterodyne, an oscillator circuit used to mix with an incoming continuous wave signal and beat it down to an audible note; (b) the detector, to extract the audio signal from the high frequency carrier; (c) the amplifier, both for the incoming high frequency signal and the detected audio or the beat signal from the heterodyne receiver; (d) regenerative feedback from the output of the detector or RF amplifier to its input, which had the effect of sharpening the tuning and increasing the amplification.
    [Show full text]
  • Electret Microphone Replacement for a Carbon Insert
    The VMARS Newsletter Issue 29 Electret microphone replacement for a carbon insert Colin Guy G4DDI When I found that I had a dud carbon insert in an H33F/PT handset, and I couldn’t find another insert that fitted (the original is about 1” diameter) I looked around for an alternative. Trevor Sanderson’s excellent article “The RAF Microphone” (Radio Bygones issue 79/80) makes reference to the use of electret inserts with an IC preamplifier in telephones and aircraft headsets, but the information given was too scant to make construction of one of these possible without reference to the IC data sheet, and the IC’s are expensive and difficult to obtain. I had a GPO type 21A insert, but the innards of this when dismantled were still too large to fit into the available space. The H33 handset is very slim, and also virtually solid, so there is very little room in which to place a preamplifier. A dig around on the internet turned up the following article written by F. Hueber, originally published in Elektor Electronics December 1994, and is published here with permission from Elektor Electronics magazine, December 1994, copyright Segment B.V., Beek (Lb.), The Netherlands, www.segment.nl. The original article included a pcb layout, but I built mine on a strip of veroboard four tracks wide by about 2” (see photo) and mounted it on the back of the ptt switch. The electret insert was acquired from a scrap telephone and all the rest of the components from TV panels. To save space the rectifier and R12 weren’t included, care being taken to ensure that the polarity was correct.
    [Show full text]
  • Note PERFORMANCE of ELECTRET IONIZATION CHAMBERS IN
    Note PERFORMANCE OF ELECTRET IONIZATION CHAMBERS IN MAGNETIC FIELD P. Kotrappa,* L. R. Stieff,* T. F. Mengers,† and R. D. Shull† The change in charge is measured using a portable charge Abstract—Electret ionization chambers are widely used for reader and is the measure of the integrated ionization measuring radon and radiation. The radiation measured in- cludes alpha, beta, and gamma radiation. These detectors do over the sampling period. These chambers are widely not have any electronics and as such can be introduced into used for measuring radon in air (Kotrappa et al. 1990) magnetic field regions. It is of interest to study the effect of and environmental gamma radiation (Fjeld et al. 1994; magnetic fields on the performance of these detectors. Relative Hobbs et al. 1996). These chambers are also used for responses are measured with and without magnetic fields present. Quantitative responses are measured as the magnetic measuring alpha and beta contamination levels (Kasper field is varied from 8 kA/m to 716 kA/m (100 to 9,000 gauss). 1999; Kotrappa et al. 1995). One feature of these No significant effect is observed for measuring alpha radiation detectors, which makes them unique, is that there are no and gamma radiation. However, a significant systematic effect electronic components or power supply associated with is observed while measuring beta radiation from a 90Sr-Y source. Depending upon the field orientation, the relative the detectors. Because of this property, these detectors response increased from 1.0 to 2.7 (vertical position) and can be used in areas with magnetic fields present without decreased from 1.0 to 0.60 (horizontal position).
    [Show full text]
  • ACCESS for Ells 2.0 Headset Specifications
    ACCESS for ELLs 2.0 Headset Specifications The table below outlines features for headsets and recording devices and WIDA’s rationale in recommending those features. Please note that WIDA does not endorse specific brands or devices. Recommended Reason for Recommendation Alternatives not Features Recommended Device: Allows for recording and playback using Separate headphones and Headset the same device. microphone increase the need to ensure proper connection and setup on the computer and thus complicate the testing site set-up. Headset Design: Comfortable when worn for a longer In ear headphones (ear buds) that Over Ear period of time by students of different are placed directly in the ear canal Headphones ages. Weight and size of headphones are more difficult to clean between can be selected based on students’ age. uses by different students. They are Portable headphones are smaller and also not suitable for younger lighter and hence may be suitable for students. Many ear buds come with younger students. Deluxe headphones the microphone attached to the are larger and heavier but have the cord, making capturing the advantage of canceling out more noise. students’ voice more of a challenge. Play Back Mode: The sound files of the assessment are Stereo recorded and played back in stereo. Noise Cancellation Noise cancellation often does not Many headsets with a noise Feature: cancel out the sound of human voices. cancellation feature require a power source (e.g. batteries or USB None connection) and hence complicate the testing site set-up. Type of Connector Some computers have two ports for Many USB-connected headsets Plug: connecting audio-out and audio-in require driver installation, but • Single 3.5 mm separately, while others have one port perform adequately for audio plug (TRRS) for both.
    [Show full text]
  • Wwciguide January 2019.Pdf
    From the President & CEO The Guide The Member Magazine for WTTW and WFMT Renée Crown Public Media Center Dear Member, 5400 North Saint Louis Avenue Happy New Year! This month, we are excited to premiere the highly anticipated Chicago, Illinois 60625 third season of the period drama Victoria from MASTERPIECE. Continuing the story of Victoria’s rule over the largest empire the world has ever known, you will Main Switchboard (773) 583-5000 meet fascinating new historical characters, including Laurence Fox (Inspector Member and Viewer Services Lewis) as the vainglorious Lord Palmerston, who crosses swords with the Queen (773) 509-1111 x 6 over British foreign policy. Websites Also on WTTW11, wttw.com/watch, and our video app this month, we know wttw.com you have been waiting for the return of Doc Martin. He’s back and the talk of wfmt.com the town is the wedding of the Portwenn police officer Joe Penhale and Janice Bone. On wttw.com, learn how the new season of Finding Your Roots uncovers Publisher Anne Gleason the ancestry of its subjects, and go behind the curtain for the first collaboration Art Director between Lyric Opera of Chicago and the Joffrey Ballet on their Orphée et Eurydice. Tom Peth WTTW Contributors On 98.7WFMT, wfmt.com/listen, and the WFMT app, the Metropolitan Opera Julia Maish on Saturday afternoons features Verdi’s Otello conducted by Gustavo Dudamel, Dan Soles WFMT Contributors Cilea’s Adriana Lecouvreur starring Anna Netrebko, Debussy’s enigmatic Pelléas Andrea Lamoreaux et Mélisande, and a new work by Nico Muhly based on Hitchcock’s filmMarnie .
    [Show full text]
  • Application Notes
    Measurement of Loudspeaker and Microphone Performance using Dual Channel FFT-Analysis by Henrik Biering M.Sc, Briiel&Kjcer Introduction In general, the components of an audio system have well-defined — mostly electrical — inputs and out­ puts. This is a great advantage when it comes to objective measurements of the performance of such devices. Loudspeakers and microphones, how­ ever, being electro-acoustic transduc­ ers, are the major exceptions to the rule and present us with two impor­ tant problems to be considered before meaningful evaluation of these devices is possible. Firstly, since measuring instru­ ments are based on the processing of electrical signals, any measurement of acoustical performance involves the Fig. 1. General set-up for loudspeaker measurements. The Digital Cassette Recorder Type use of both a transmitter and a receiv- 7400 is used for storage of the measurement set-ups in addition to storage of the If we intend to measure the re- measured data. Graphics Recorder Type 2313 is used for reformatting data and for ., „ J, ,, „ plotting results sponse of one of these, the response ol the other must have a "flat" frequency response, or at least one that is known in advance. Secondly, neither the output of a loudspeaker nor the input to a micro­ phone are well-defined under practical circumstances where the interaction between the transducer and the room cannot be neglected if meaningful re­ sults — i.e. results correlating with subjective evaluations — are to be ob­ tained. See Fig. 2. For this reason a single specific measurement type for the character­ ization of a transducer cannot be de- r.- n T ,-,,-,■ -.
    [Show full text]
  • The Early Years of the Telephone
    ©2012 JSR The early years of the telephone The early years of the telephone John S. Reid Before Bell Ask who invented the telephone and most people who have an answer will reply Alexander Graham Bell, and probably clock it up as yet another invention by a Scotsman that was commercialised beyond our borders. Like many one line summaries, this is partly true but it credits to one person much more than he really deserves. Bell didn’t invent the word, he didn’t invent the concept, what ever the patent courts decreed, and actually didn’t invent most of the technology needed to turn the telephone into a business or household reality. He did, though, submit a crucial patent at just the right time in 1876, find backers to develop his concept, promoted his invention vigorously and pursued others through the courts to establish close to a monopoly business that made him and a good many others very well off. So, what is the fuller story of the early years of the telephone? In the 1820s, Charles Wheatstone who would later make a big name for himself as an inventor of telegraphy equipment invented a device he called a ‘telephone’ for transmitting music from one room to the next. It was not electrical but relied on conducting sound through a rod. In the same decade he also invented a device he called a ‘microphone’, for listening to faint sounds, but again it was not electrical. In succeeding decades quite a number of different devices by various inventors were given the name ‘telephone’.
    [Show full text]
  • How to Make an Electret the Device That Permanently Maintains an Electric Charge by C
    How to Make an Electret the Device That Permanently Maintains an Electric Charge by C. L. Strong Scientific America, November, 1960 Danger Level 4: (POSSIBLY LETHAL!!) Alternative Science Resources World Clock Synthesis Home --------------------- THE HISTORY OF SCIENCE IS A TREASURE house for the amateur experimenter. For example, many devices invented by early workers in electricity and magnetism attract little attention today because they have no practical application, yet these devices remain fascinating in themselves. Consider the so-called electret. This device is a small cake of specially prepared wax that has the property of permanently maintaining an electric field; it is the electrical analogue of a permanent magnet. No one knows in precise detail how an electret works, nor does it presently have a significant task to perform. George O. Smith, an electronics specialist of Rumson, N.J., points out, however, that this is no obstacle to the enjoyment of the electret by the amateur. Moreover, the amateur with access to a source of high-voltage current can make an electret at virtually no cost. "For more than 2,000 years," writes Smith, "it was suspected that the magnetic attraction of the lodestone and the electrostatic attraction of the electrophorus were different manifestations of the same phenomenon. This suspicion persisted from the time of Thales of Miletus (600 B.C.) to that of William Gilbert (A.D. 1600). After the publication of Gilbert's treatise De Magnete, the suspicion graduated into a theory that was supported by many experiments conducted to show that for every magnetic effect there was an electric analogue, and vice versa.
    [Show full text]