At higher frequencies the phase-difference (time delay) between your ears would mean you’d only get cancellation in one ear at a time. With no room reflections you can probably get 100% cancellation at low frequencies. …If you have 3 speakers, it might be easier to calculate the wavelength and set the distance (between you and the speakers) for 1/3rd of the wavelength. At 10kHz the wavelength is a little less than 1.5 inches, so 1.5 inches is 360 degrees and there’s a phase-difference between your 2-ears and simply moving your head will make a difference. …If you have a normal stereo set-up and reverse the connections to one speaker (180 degree phase inversion), you’ll get a LOT of bass cancellation but you’ll still hear some bass.* And, you’ll get enough cancellation at other frequencies to make music “sound weird”, especially as you move around.Īt higher frequencies it will be more-dependent on your location, the location of the speakers, and reflections in the room. In theory you could get perfect cancelation (at any frequency) but the acoustic waves won’t match perfectly, especially if you are in a “normal room” where sound bounces-around. Buy Bogen TG4C - Multiple Tone Generator for Paging Systems featuring Four Tones, External Triggering, Two-Burst or Continuous Tone, Level and Pitch Adjust. It seems I have to have 3 separate speakers.Īt low (bass) frequencies you’ll get partial cancellation when the sound waves mix in the air. To generate a sine tone at 440 Hz, that has the same duration as the selection, with a starting phase of 120 degrees: (osc (hz-to-step 440) 1 *sine-table* 120) So, for example, to generate a sine tone at 440 Hz, that has the same duration as the selection, with a starting phase of zero: (osc (hz-to-step 440) 1 *sine-table* 0) ![]() “pitch” can be thought of as the note number, and there is a simple way to convert from “frequency” (in Hz) to “pitch”, using the “HZ-TO-STEP” function: īy default the Nyquist prompt treats the selection as a duration of “1”. Where “duration”, “table” and “phase” are optional parameters. The command “OSC” can generate a variety of simple tones, the default being a sine tone: īy default the Nyquist Prompt uses LISP syntax, so the command is: (osc pitch ) When used as a telephone receiver and transmitter, actual tests have shown that the reproduction of sound is remarkably faithful.Probably the easiest way is to use the Nyquist Prompt effect: Since it gives a pure tone of constant and measurable pitch and intensity over a wide range, it would serve as a precision source of sound, useful both for research and lecture purposes. Measurements of the amplitude for various frequencies agreed well with the calculated values. By increasing both direct and alternating currents five-fold, the output could be increased over six hundred-fold. ![]() in diameter, a direct current of 1 ampere, an alternating current of 0.085 ampere, and a frequency of 10 5 2 π, these were respectively 7 × 10 − 7 cm., and 9 ergs per second. The distribution of the magnetic field between the coils was determined experimentally the diaphragm current equations were deduced and solved for a particular case the forces on various parts of the diaphragm were calculated, and thence the amplitude of vibration and the sound energy output. (2) Quantitative study of the performance. When used as a receiver of sound, the current generated in the coils by the motion of the diaphragm is fed into a thermionic amplifier. When used as a generator of pure tones, the coils were connected in the circuit of a thermionic oscillator whose frequency could be varied from 500 to 25,000 vibrations per second. The aperiodicity of the diaphragm renders the calculation of the performance of the instrument practicable, and eliminates distorsion, due to resonance, in the wave form of the emitted sound when the instrument is excited by a complex alternating current. ![]() The absence of overtones is due to the absence of ferromagnetic material, and to the fact that the radial magnetic field is constant. For low frequencies the electrodynamic force is approximately proportional to ω I 0 I sin ( ω t + θ ) and the amplitude of vibration is approximately proportional to I 0 I ω. The instrument consists of a thin, non-magnetic, metallic diaphragm between two flat coils through which a constant direct current I 0 flows in such a way as to produce a radial magnetic field in the diaphragm then when a simple harmonic alternating current I of the frequency ω 2 π is superposed upon the direct current, circular currents are induced in the diaphragm, which thereupon is acted upon by a simple harmonic electrodynamic force and vibrates with the frequency of the alternating current. New Pure Tone Generator and Receiver of Sounds.-(1) Construction and operation.
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