Since the end last semester, some residents of Davis and Hayden halls have been complaining about a mysterious noise coming from the Hudson River.

This noise comes from a SODAR (Sonar Detection and Ranging) instrument being used to measure wind speeds. The instrument emits a sound pulse in several directions, which has its speed changed by particles in the air. By measuring the phase shift in the sound, both the direction and speed of the wind can be measured.

The purpose of the project is to study wind shear in urban environments, which can be used to help predict urban dispersion. The research has domestic security applications, particularly in predicting the dispersion of an airborne bio-weapon or fallout from a dirty bomb.

The project would likely have gone unnoticed by most Stevens students, except for a periodic noise it emitted, which could be heard in rooms in both Davis and Hayden halls. "It's really annoying," said Katie Hibner '08, a Davis resident. "It's worst when getting to bed, because ... it's one of the few things you can still hear."

The fact that the start of the project coincided with the start of finals was a problem for some. "Normally this wouldn't be a problem, but since it was time to study for finals, everyone was quiet and it could be easily heard while studying and going to sleep," remarked Keith Cassidy '09.

The noise affected some people enough to organize a group to find the source of the noise. On December 12, a group of between 40 and 50 students went up the Howe Center to complain about the noise. The students were told that the Office of Residence life would investigate the cause of the noise.

Davidson Lab has not been unresponsive to the complaints. According to Brian Fullerton, a research engineer in Davidson Lab, the Office of Residence Life asked the lab to turn the instrument off during last semester's final exam period. "We had a technical issue that IT was helping us resolve at the time, so we decided it was an easy request to grant until we cleared up our communications issue."

Over intersession, the device was turned on again, and Residence Life once again contacted the lab about the noise, particularly at night. In response, the power output has been halved from 8pm to 8am, and reduced by 10% during the day. "I hope this is a solution we can all live with," said Fullerton.

Recently, though, the noise has not been a problem. "I don't think there is a noise any more," commented Hibner. This is because the device has been temporarily shut off. "We will be testing new locations over the next week or so," said Michael Bruno, Director of the Center for Maritime Systems.

The SODAR device is part of an atmospheric research project being conducted by Davidson Laboratory and the Stevens Center for Maritime Systems, partnered with Brookhaven National Laboratory and Pacific Northwest Research Laboratory.

The data collection portion of the project is expected to continue into April, while the temperature remains low, with analysis of the collected data going on long after that.

This type of device is particularly new, with only a few currently being used worldwide. It is believed, however, that within a few years, SODAR devices will become common weather instruments.