Motion Picture News (Oct-Dec 1929)

40 Motion Picture News December 7, 192& Layman'* Terms Engineer's Terms Cause Roughness, Scratchiness Surface Noise 1. Worn Needle 2. Faulty Wax 3. Faulty Film 4. Dirt in Sound Gate Booming, Blaring Speaker or Horn Resonance 1. Overloading 2. Faulty Construction Dullness, Lifelessness Frenquency Distortion Uneven Response — Frequency Characteristic Predominance of Low Notes — Upper Frequencies"Going Bass" "Washed Out" Voices Unnatural — Chrillness, Sharpness, Harshness Lower Frequencies"Washed Out" 1. In Recording Apparatus 2. In Reproducing Apparatus 3. In Horns 4. Selective Absorption in House Change in Quality or Character of Sound Phase Distortion — Uneven Energy — Response, etc. Uneven Response-Intensity Characteristic — 1. In Recording Apparatus 2. In Reproducing Apparatus 3. In Horns Sound and Picture "Out of Step" Faulty Synchronization 1. Film or Record Started Wrong 2. Faulty Recording Sound Does Not Come From Faulty Illusion Screen Faulty Horn Placement Echo Sound Too Loud Faulty Loudness Distribution Bad Fader Adjustment Sound Muffled Faulty Loudness Distribution Excessive Use of Absorbent Material Incorrect Placing of Horns Tremolo Flutter Flutter Faulty Recording Faulty Loop Adjustment Vibration of Exciting Lamp Faulty Speed Control Stuttering Mouthing Words Faulty Illusion Echo Pronounced Secondary Reflection Out of Phase with Direct Sound Resonance, Echo, Lingering, Blurring, Confusion, Sound Builds Up; Liveliness Reverberation Too Great Duration of Resid ual Sound Due to Lack of Sound Absorption in Room Masking, Interference, Gen Extrfmeous Sound era! None Street Noise, Fan Noise, Projection Booth Noise, People Moving, etc. r> a =_«*. i „„= „f !„♦.! This may aPP'y t0 anv condition where the hearing is unD1-km£ satisfactory. It may be due to almost any of thi above hglbuity cauaes ONE of the greatest difficulties that the sound picture industry has to face is the lack of an adequate vocabulary on the part of the unscientific listener. Even those theatre men who are careful enough to listen and criticize faulty reproduction or defective acoustics seldom are able to express themselves in language intelligible to the engineers. Probably because the organs of sight are used so much more frequently than the organs of hearing, the average individual is much better equipped to describe the former type of sensation. Each newdevelopment of civilization, however, demands more and more of the ear. It seems desirable, therefore, to try to develop a terminology which will be intelligible to people of all classes in order that sound reproduction may be opened to intelligent criticism. Such terminology is available, but it is to be found only in technical books or papers, or in the laboratory jargon of the engineers. For ex ample, what the acoustical engineer calls reverberation the average individual usually calls echo. What the engineer defines as echo is most often described by the listener as a "dead spot." And this so-called dead spot is normally produced by a form of resonance which the ordinary person is quite likely to call reverberation ! The following paragraphs are a preliminary attempt on the part of the writer to bring the theatre-man and the sound engineer to a common ground. Let us assume, then, that we are attending a sound picture. Or if we own the theatre perhaps we are standing in the back of the house trying to determine how it is "going over," and what defects may be in evidence. Probably the condition which we are most likely to observe is that there is something wrong with the volume of the sound, (faulty loudness distribution is the technical term). If there is too much sound it is The Acoustical Vocabulary Translated for the Showman By John S. Parkinson Staff Acoustical Engineer, JohnsManville Corp. in all likelihood due to an incorrect adjustment of the "fader," a volume control which is operated from the projection booth. The adjustment should really be made from the floor of the house, preferably in the center, by a person stationed there to signal the projection booth. If there is not enough sound, that is, if the speech or music sounds muffled or dead, it may again be due to an incorrect "fader" adjustment, but is more likely due to the acoustics of the house. The shape of the house may be such that sound does not reach all parts in proper proportion, or there may be too much absorbent material present. The former condition is often produced by a deep over-hanging balcony. Sound can only enter through the throat of the balcony, and by the time it has passed over a number of rows of people or upholstered seats absorption has considerably reduced the amount of energy available to the ear. It may be worth while at this point to digress for a moment and explain this phenomenon of sound absorption. Sound, like heat, light, electricity, etc., is a form of energy. It may be converted into other forms of energy under certain conditions. Thus, as light energy disappears as such when it strikes a dull black surface, sound also disappears when it strikes a certain type of surface. The phenomenon is not actually one of absorption, but of conversion into heat or some form of kinetic energy. Most people have encountered it in some form or another, as in a closet full of clothes or in a room piled high with rugs or furniture. In direct contrast is the effect produced in the empty rooms of an unfurnished house or between theatre walls or a hospital corridor. Absorption is produced by the porosity or flexibility of the