In Everyday Language

Radio Record, Volume III, Issue 49, 20 June 1930, Page 7

In Everyday Language

VALUABLE TESTS © FROM 2YA

Oe ee F requencies, Overtones and Harmonies

N Saturday, June 21, two frequency tests will be carried out by 2YA -one under daylight conditions at the close of the broadcast of the First Test, and the other under night conditions, at 10° o’clock. These broadcasts will give listeners an opportunity of testing out the capabilities of their recéivers. The -sensation of hearing is caused by sound waves which enter the ear, impinge on the membrane or drum, and set up vibrations which register in the brain. Different frequencies affect different parts of the membrane, creating the sense of tone, noise, harmony, speech-all depending on frequency, although differences in structure or sensitiveness in different human ears cause two persons to give different interpretations to the same sound. The range of frequencies that the human ear can detect varies considerably, the average being from 16 to 15,000 cycles per second. Only the radio receiver that reproduces truly can live. When an art is young we suffer imperfections, but behind the scenes men are strivingsome to give the public what it thinks it wants, a whim of the moment; others to give perfection, a lasting monument. Faithful reproduction entails a perfect radio receiver. A simple formula, but in the term "faithful reproduction" there are many factors, and frequency range is not the least important. Frequency Range. ‘OTES of music and speed? consist of a fundamental frequenhey with various harmonics and over-tones. The character of the music, the type of instrument, different words, letters, ete, depend upon the harmonics, but the pitch depends upon the fundamental frequency. Musical instruments and voices have definite fundamental range. The male voice fundamental frequency averages around 120 cycles per second, while the female fundamental voice frequency is about 240 cycles, an octave higher. However, over-tones exist in some speech sounds up to 8000 per second, for while female speech has less over-tones than male, they extend up to 8000, and the richest over-tone area of the male voice is between 3000 and 5000 cycles per second. It is these differences in the number and combination of harmonics and overtones that enable the human. ear to distinguish between different persons’ voices. Likewise, it is these different harmonic combinations that enable the human ear to

distinguish between a violin, ‘clarinet, french horn, piano, ete., when each instrument sounds or plays the same note on the chromatic scale of music. A ’cello solo may sound on some sets over some stations as a natural violin or saxophone would sound to the same human ear. Many obsolete and present-day inferior receiving sets (transmitting sets, as well) cut off the higher frequencies. Cutting to 6000 eliminates the characterising features of the unvoiced sounds such as s, f, sh, th, z, etc., especially in the upper reaches of the female voices. This, of course, accounts for the disapproval of worthy soprano. voices over earlier limited receiving sets. In cutting off the low frequencies. tone colour.or timbre is lost. ' Timbre is very important in music, as it is one of the factors that define the various instruments. The fundamental and the first three or four overtones are the distinguishing features. On the

other hand, if too many higher overtones are lost, "brilliancy" and "definition"’ disappear. Drums have fairly low fundamental, but are particularly rich in higher harmonies; cutting these high overtones renders their reception dull and dead. The organ, harp and piano have a fundamental range from 16 to 4000 eycles, and, as the chief characterisation of all these is a strong first octave, frequencies up to 5000 and somewhat is)

above should be unimpeded for good definition. The ranges of voices and instruments are set out in the accompanying table: HERB are many limiting factors in radio, some of which can be overcome. Some sets emphasise bass by sacrificing harmonics. There is really no more bass; the apparent tone is merely lowered. There are many extraneous noises which are caused by poorly constructed parts. On many sets the higher overtones down to 5000, and in a few cases.even down to 4000, are cut off deliberately at the speaker. The untrained ear enjoys this overpronounced depth-for a little while. Other manufacturers use no limitative devices on the speaker, and are constantly striving to extend the frequency range up and down, relying on the increasing demand of a public rapidly becoming educated to perfect reproduction, which it has been found among other things equals reception of all frequencies from the fundamental even unto the third and fourth harmonic. Clarity seems to be a stock selling argument, and, of course, clearness is desirable. It is, however, merely a result of proper design. Many obsolete sets gave forth "clear’ sounds. Clarity without frequency range {s not good music. A policeman’s whistle can sound clear, but would give a ven poor rendition of "Lohengrin."

Lowest Highest Funda- Fundamental, mental. Organ ececce 16 4000 Piano eccVeccn 26 4096 Bass viol .oo.e 40 240 Bass tuba ...0- 42 342 Bassoon ..c0c0 60 480 ’Cello eseccee 64 682 Bass clarinet .. 8 . 480 Trombone .... is 480 Bass voice .- 80 342 Kettle drums ... 84 170 Baritone voice 96 384. French horn ... 106 860 Tenor voice .... 128 480 Viola eccoecoe 128 1152 Trumpet coce 160 960 Clarinet coos 160 1536 Alto voice .... 170 682 Violin evceoeo 192 3072 Soprano voice .. 240 1152 Oboe eesccoee 2G 1536 Flute ecoosess 206 2304 Piccolo ....... 542 4608

Fundamental Ranges.