Accession Number : ADA192203
Title : Higher Frequency Ambient Noise in the Arctic Ocean.
Descriptive Note : Technical rept. 1 Jan-31 Dec 87,
Corporate Author : SCIENCE APPLICATIONS INTERNATIONAL CORP COLLEGE STATION TX
Personal Author(s) : Lewis, James K ; Denner, Warren W
PDF Url : ADA192203
Report Date : Jan 1988
Pagination or Media Count : 28
Abstract : Higher frequency (1000 Hz) arctic ambient noise episodes during non-summer months were used to study generating mechanisms. In most cases, thermal fracturing of sea ice was responsible. A suite of heating and cooling processes that relate to thermal fracturing of sea ice were considered. Numerical simulations with a daily heating cycle and no snow cover implied that maximum noise levels occurred at 1900 hrs local. Radiational heat balances are more important than sensible heat flux in producing fracturing of sea ice. With snow cover, the amount of ice fracturing is reduced. A daily heating cycle produces maximum fracturing at 0300 to 0800 hrs local, a common feature seen in observed noise data. Simulations were made using observed Arctic Ocean solar radiation, air temperature, wind speed, albedo, and cloud cover from the spring of 1976. The agreement between the model ice fracturing parameter and the observed 1000 Hz noise levels was excellent. However, results indicate that blowing snow and ice fog may be additional factors in the heat flux balance of sea ice. The short space scales of higher frequency, arctic ambient noise are likely a result of spatial variations in snow cover. The short time scales of such noise are not only a result of multiple noise-generating processes but also changes in cloud and snow cover. Results indicate that thermal fracturing of sea ice can produce broad-band noise. There are clear examples of 32 Hz noise variations associated with thermal fracturing of sea ice.
Descriptors : *AMBIENT NOISE, *ARCTIC OCEAN, *SEA ICE, *NOISE(SOUND), *CRACKING(FRACTURING), ALBEDO, ARCTIC REGIONS, ATMOSPHERIC TEMPERATURE, BALANCES, BROADBAND, CLOUD COVER, COOLING, CYCLES, DAILY OCCURRENCE, HEAT, HEAT BALANCE, HEAT FLUX, HEATING, ICE FOG, LEVEL(QUANTITY), NOISE GENERATORS, NUMERICAL ANALYSIS, RADIATION, SCALE, SHORT RANGE(TIME), SNOW, SNOW COVER, SOLAR RADIATION, SPATIAL DISTRIBUTION, WIND VELOCITY
Subject Categories : Acoustics
Distribution Statement : APPROVED FOR PUBLIC RELEASE