Combination Tones: An Objective Analysis
Abstract: The purpose of this study was to collect descriptive data on difference tone perception, and to determine if these tone phenomena exist as physical entities in the environment. Effects of music training, and the interval frequency between sounding primaries were also determined from analyses of descriptive data. The investigation was divided into a two-fold process. First, the perception of difference tones by human subjects was investigated. Subjects were instructed to listen for a tone lower than a pair of primary frequencies. When the difference tone was heard, subjects attenuated it until inaudible. Second, difference tones were analyzed as environmental events by using the same primary frequencies employed with human subjects. Four microphones were presented with 70 dB tones, and measurements were made of the intensity magnitude of the difference tone event. Average level of difference tone detection for music majors was 70 dB, and for nonmusic majors, 68 dB. The average intensity difference music majors withstood prior to perceptual loss of difference tones was 26.5 dB, and for nonmusic majors, 31.5 dB. It was concluded that difference tone perception was not dependent on equal intensity of the two primaries. Each microphone detected the difference tone with a mean detection level of 26 dB. These data indicated that the difference tone exists as a physical entity of the environment at a level 40 dB below the 70 dB primaries.
Keyword(s): combination-tones, tone, perception, music-perception, music-students, difference-tones.