1983 The Anstendig Institute


It is now well known that any reproduction of sounds entails distortion in the balance of the different frequencies in relation to each other. This distortion is caused both by the reproduction of the sound and by the characteristics of our own hearing. Mechanically registering sounds entails many stages from the microphone, through the tape machine, to the playback medium (tape or records), to the playback electronics, to the speakers and finally to the room and to the listener, whose body must mechanically register the sounds before he hears them (we do not hear the sound source, we hear the vibrations of our own bodies which are caused to vibrate by the vibration from the sound-source1). Each one of these mechanical stages usually changes the balance of the frequencies, some drastically. In other papers, The Anstendig Institute has pointed out that, in sound-reproduction, the overtones of the original sounds become fundamentals in playback and produce their own set of overtones, causing a massing of overtones that blurs the sound.2 They also point out that we do not hear all frequencies equally loudly and that the way we hear the balance of the frequencies changes in relation to the overall volume level. In other words, if sound is reproduced with the volume controls set at any particular level, we do not hear the frequencies in the same balance to each other as they are reproduced by the speaker. We hear some frequencies louder than others; and the ratio of this imbalance in the way we hear frequencies changes if we change the overall volume level using the master volume control. This fact has long been known and many graphs of the distortions of our hearing at most volume levels have been made, one of which is attached to this paper.

The fact that our hearing along with the process of sound-reproduction distorts the frequency-balance of the original clearly means that, if one wants to achieve natural-sounding reproduction, one must compensate for these distortions by changing the balance of the frequencies to each other during playback.3 Although known since the early 1930's, this fact of life has been ignored, mainly because adequate means of correcting these frequency imbalances were not yet available. In the meantime, other technical aspects of sound-reproduction have been perfected to a degree where most better components can now reproduce a sound signal with good fidelity, and some components achieve truly high accuracy. But all sound-enthusiasts know that, despite the technical advances, recordings still do not sound like the original, live event. The obvious missing link is the lack of compensation for the frequency imbalances. The Anstendig Institute has found that, with high quality equipment, correct equalization of the program material for the listener and the listening circumstances is the only remaining problem in the way of truly natural, undistorted, sound-reproduction.4


Unfortunately, there is, at present, no possible way the owner of a sound-system can have natural, undistorted sound-reproduction without achieving it for himself by acquiring the requisite equalizers and painstakingly learning how use them correctly. If there were strict industry standards for the characteristics of recordings and components, and if owners of sound-systems would have their systems adjusted for correct frequency response in their listening room, it would be possible to pre-equalize all recordings to sound correct at a given reference volume level; but for the time being the listener has to equalize his recordings himself.

Learning how to equalize recordings demands learning how to hear sounds in a completely new way. One must learn how to recognize frequencies ranges instead of pitches. Although a pitch is named by the dominant frequency (A = 440 cps, for example), the actual sound really consists of many more frequencies above and below the named pitch, many of which rival the named frequency in loudness. In sound-reproduction and also in adverse acoustical situations, a sound can consist more of those other frequencies than of the actual pitch being played (San Francisco's Davies Hall has this problem, with the sound of many instruments such as the tuba and tympani suffering from exaggeratedly loud overtones). Learning to hear frequency ranges so that one can recognize when they are exaggerated and then equalize them demands a whole new orientation of one's hearing. Hearing is an acquired skill. One only recognizes what one is familiar with, and, since it has been impossible until recently to listen to the various frequency ranges individually to hear what they sound like, we have no frame of reference that allows us to recognize them. The only way to learn how to recognize them, is to practice doing so with equalizers (1/3 octave equalizers are best for this), which would be accomplished by playing recordings of music that uses the full range of frequencies (orchestra tuttis, for example), separately isolating each frequency band, and studying what it sounds like. This would be done by boosting the volume of the frequency band one wants to observe while cutting the rest of the bands. When one has some familiarity with the sound of the various frequency ranges, one can try equalizing the program material.5 After a few attempts at program equalization, one will have noticed that, when a range of instrumental notes seems too loud, the frequency band that has to be reduced in order to clarify and balance the sound is often far distant from the frequencies of the actual written notes. This is the reason why one has to develop a new manner of hearing.

The possibilities of equalization range from simple equalization that eliminates the harshest, most irritating frequency distortions, to fine, delicate balancing of the sound that rivals that of the conductors and musicians in the actual performance. But the distortions in recorded sound generally occur in frequency ranges to which we are most sensitive and which cause us tangible physical irritation. Equalization can make a big difference just by eliminating the most irritating imbalances that keep one from relaxing into the flow of a performance.

Sound is the most potent influence on us and music has long been recognized as the most powerful of the arts. The whole world in one way or another uses and depends on recordings; yet, without equalization, we cannot accurately reproduce sounds. One of the great treasures of the world is our recorded legacy of performances by the greatest musicians and actors of this century. Extraordinary experiences are contained in those recordings, but without equalization it is impossible to hear them accurately. The expression of the performance itself is falsified, and we thus do not have those extraordinary experiences. The effort necessary to equalize one's recordings is substantial, but there is no other, easy way of achieving lifelike sound reproduction.


1 This point is explained in various papers of The Anstendig Institute.

2 See our paper "The Massing of Overtones in Sound Reproduction."

3 The balance of frequencies in any given situation is called the "equalization", changing the balance of the frequencies is also called "equalization", and the machines used for that purpose are called "equalizers.

Equalizers are machines that divide the frequency-spectrum into equal divisions (most often octaves or 1/3 octaves) with a separate control for each division (band) that allows the volume level of that portion of the frequency range to be changed in relation to the others. It is essentially an elaborate, ideal tone-control.

4 See our papers on sound equalization.

5 The Anstendig Institute is working on another paper explaining in detail how to equalize.

Papers on related subjects are available free of charge on request.


The Anstendig Institute is a non-profit, tax-exempt, research institute that was founded to investigate the vibrational influences in our lives and to pursue research in the fields of sight and sound; to provide material designed to help the public become aware of and understand vibrational influences; to instruct the public in how to improve the quality of those influences in their lives; and to provide the research and explanations that are necessary for an understanding of how we see and hear.