Showing papers on "Noise published in 1968"

Effect of Signal Duration on Detection for Gated and for Continuous Noise

Abstract: A series of two‐alternative forced‐choice experiments showed that for short durations, the detection of a tonal signal in noise when the two are gated synchronously is superior to the detection of the signal in a background of continuous noise. The experiments also showed that for gated signal and noise, there is a steady improvement in detection as the duration is shortened, provided that highly practiced observers are employed in the task. Naive observers exhibit a similar trend, but their performance drops at the short durations (5 and 10 msec) where the listening task becomes very difficult.

American Conference of Governmental Industrial Hygienists' Proposed Threshold Limit Value for Noise

Abstract: The American Conference of Governmental Industrial Hygienists has proposed a Threshold Limit Value for Noise. The limit for broad band noise would be 92 decibels, as measured on the A-scale of a sound level meter (dBA), for exposure of 4 to 8 hours per day; 97 dBA for 2 to 4 hours; 102 dBA for 1 to 2 hours; and 107 dBA for less than 1 hour. The limit for narrow bands of noise or pure tones would be 5 decibels lower than that for broad band noise. A limit of 140 decibels peak sound-pressure level for impulsive or impact noise is recommended.

Comments on “The Use of Noise Bands to Establish Noise Pitch” [H. R. Rainbolt and E. D. Schubert, J. Acoust. Soc. Am. 43, 316–323 (1968)]

Abstract: In their paper, Rainbolt and Schubert incorrectly attribute at related pilot study to me owing to misrecollection of a letter from me to Schubert in 1963. The personal communication in question and did not represent the study as mine but as a student experiment performed by three graduate students of my acquaintance 3 yr before t heard about it in 1960 and 6 yr prior to my letter to Schubert. It is pointed out here that I did not give permission to cite or publish the data of others. My communication to Schubert indicated that the preliminary experiment, despite its possible importance if confirmable, had certain enumerated limitations, that should now influence the weight attached to it. The 1963 letter also directed attention to the pitch judgments of one subject, which are pertinent to points raised by Rainbolt and Schubert.

Intermittent Noise and the Brain Waves

Abstract: This experiment was carried out to investigate the arousal states in the brain by the measurement of the brain waves, especially the alpha-wave (8∼13c/s) appearance under exposure to continuous and intermittent noise.Sixteen healthy men of 20 to 34 years of age were exposed to white noise of 80dB (C) under three different conditions, that is, (1) continuous noise for 10 minutes, (2) regular intermittent noise of one-minute noise and one-minute rest for 19 minute periods, (3) irregular intermittent noise of one-minute noise and irregular rests for 19 minute periods. The duration of the noise exposure in the three conditions each totaled ten minutes.Brain waves were recorded for 10 minutes before exposure to noise, during the noise administration of 10 or 19 minutes and for 10 minutes after the exposure. The changes of alpha-wave appearance between pre- and post-exposure were compared.The results obtained were as follows:1) The appearance of the alpha-wave decreased significantly in the ninth and tenth minutes after exposure to continuous noise.2) Exposure to regular intermittent noise resulted in a significant decrease of the alpha-wave appearance in the latter half of the noise administration.3) Exposure to irregular intermittent noise caused a significant decrease of the alpha-wave appearance after the first half of the noise administration.4) Comparing regular and irregular intermittent noise, the latter brought about a stronger alpha-blocking during the noise administration, while the former showed a delayed restoration in alpha-wave appearance after exposure to noise.These results indicate that the influences of noise as a stressor differ not only by amount of physical energy, but also by regularity of generation.