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Audio, IRE Transactions on

Issue 4 • Date July-August 1961

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Displaying Results 1 - 13 of 13
  • [Front cover and tabel of contents]

    Page(s): 0
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  • Message from the new chairman

    Page(s): 97
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  • The editor's corner

    Page(s): 98
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  • National officers of the PGA, 1961-1962

    Page(s): 99 - 101
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  • Chapter news

    Page(s): 102
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  • PGA awards for 1960

    Page(s): 102
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  • More on nonlinear distortion correction

    Page(s): 103 - 105
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    Further consideration is given to basic amplitude limitations which may apply to the complementary distortion method of nonlinear distortion correction. It is found, in disagreement with others, that points at which the differential gain is zero or infinite do not limit the amplitude over which complete correction is possible but that relative maxima, minima, gain zeros, and infinite-gain points in the characteristic do set limitations when the usual simply connected tandem configuration is employed. When the characteristic to be corrected is multiple valued or passes through points of zero or infinite gain within a given amplitude range, a multiply connected correction circuit must be used for perfect correction of distortion over the amplitude range in question. View full abstract»

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  • A simplified noise theory and its application to the design of low-noise amplifiers

    Page(s): 106 - 108
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    Any noisy amplifier can be represented by an equivalent noiseless amplifier plus two noise generators either at the input or the output of the amplifier. The choice of two particular noise generators (the equivalent short-circuit noise voltage and the open-circuit noise current) to characterize a noisy amplifier has a number of advantages over the concept of noise figure. The noise generators can easily be measured separately from the source noise, and the optimum source impedance and the noise figure at any source impedance can then be calculated. Since the amplifier noise is measured separately from the source noise, low noise figures can be easily measured. The optimum source impedance equals the quotient of the two noise generators, and the noise figure depends upon their product. Neither feedback nor input impedance is a consideration in determining noise figure and optimum source impedance. Several transistor noise diagrams show how the two noise generators are affected by emitter current, collector voltage, and frequency. Noise diagrams can be used to select the most suitable amplifying devices and optimum operating conditions for various applications. View full abstract»

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  • Average vs RMS meters for measuring noise

    Page(s): 108 - 111
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    It appears that the controversy is still alive over whether average reading or root-mean-square reading meters should be specified as standard for the measurement of noise. This being the case, it is worthwhile to consider the entire subject from the standpoint of basic fundamentals, to determine what are the significant quantities involved, and then proceed to investigate which type of meter yields the most significant results. The following is the result of such an investigation. The entire discussion rests on 1) an axiom, that energy transfer is the fundamental interaction within the universe, and 2) a premise, that for the type of measurements under discussion (audio), all significant processes are linear. Given these two starting points, the conclusion is reached that the meaningful quantities are found by rms measurements. It is shown further, by concrete example, that measurements made with average reading meters can depart widely from those made with an rms meter. This being the case, it is necessary that measurement standards specify the use of rms meters. Those who elect to use average meters, then, bear the responsibility of determining the accuracy of their results in terms of the fundamentally important quantities. View full abstract»

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  • An adjustable shelf-type equalizer with separate control of frequency and limiting attenuation or amplification

    Page(s): 112 - 117
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    This device provides for control of the high-frequency content of an audio program, allowing the operator to choose independently: 1) the frequency above which equalization is to occur, and 2) the maximum correction in signal strength which results in the range of frequencies under correction. Three operating controls are used. One control determines whether the high-frequency signals shall be increased, left unchanged, or decreased in strength relative to the low-frequency signals. A second control is calibrated in terms of the frequency above which correction shall occur. The third control adjusts the asymptote which represents the maximum correction which shall occur for frequencies considerably higher than that chosen by the frequency control described above. The circuit can be described briefly as follows: for high-frequency attenuation, the operation employs a negative feedback amplifier whose output may have high-frequency loss inserted by an RC network following the amplifier; for high-frequency boost, the RC network is inserted in the amplifier feedback path so that the amplifier output (which now becomes the system output) has a rising high-frequency response which corresponds to the attenuation of the RC network. All three controls are continuously adjustable within their ranges of operation. View full abstract»

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  • "Apparent bass" and nonlinear distortion

    Page(s): 117 - 121
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    A discrepancy between the "apparent bass" response heard by the average music listener and anechoic-chamber measurements has been noted for some small loudspeaker systems. This may be caused by the psychoacoustic response to the generation of harmonic distortion by the nonlinear suspension and the inhomogeneous flux gap density in a small speaker. An electrical analog, with controllable distortion, of such a speaker has been subjected to listener tests and evaluation to determine if this is the cause of the apparent bass effect. An analysis of the listener reactions to various music stimuli through the system indicates that this is the case. View full abstract»

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  • The concept of linear interpolation in spectral compensation

    Page(s): 122 - 131
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    Spectral compensation is usually achieved with equalizers cascaded so as to generate a desired response. In the concept of linear interpolation, a series of points are located along the desired response and linear interpolation provided between adjacent points. This is accomplished with contiguous band-pass filters arranged so as to minimize the effect of filter crossover. The performance limitations depend upon the filter characteristics, crossover ripple, and the type of response to be equalized. This approach to compensation has two advantages. First, automatic control of the spectrum can be achieved when the input signal is a random noise voltage. Second, discreet points on the frequency axis permit control using digital techniques. Data is presented for some cases of peak-notch resonances encountered in acoustic and vibration systems. View full abstract»

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  • [Back cover]

    Page(s): c4
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Aims & Scope

This Transactions ceased production in 1962. The current retitled publication is IEEE Transactions on Signal Processing.

Full Aims & Scope