Joe H. Mullins
Dept. of Mech. Eng., Univ. of New Mexico, Albuquerque, NM 87121
Sandia Natl. Labs., Albuquerque, NM 87185-5800
Persistent complaints of an annoying low-frequency sound in Northern New Mexico, particularly in the vicinity of Taos, led to a request by members of the Congressional delegation of NM for an investigation. During the summer of 1993, in Taos, extensive simultaneous measurements were carried out of acoustic, seismic, electric, magnetic, and electromagnetic signals by a team from Sandia and Los Alamos National Laboratories, the Air Force Phillips Laboratory, and the University of New Mexico. Since anecdotal evidence and signal matching tests by the hearers implicated the frequencies between 30 to 100 Hz, special attention was given to that range. However, no signals were found matching the description, and in particular no airborne audio signals in this range were found other than background, even though the acoustical detector was capable of measuring signals less than -50 dB SPL. Subsequent complaints of similar sounds from widely distributed areas in the U.S., and a long history of these in the U.K. [R. N. Vasudevan and C. G. Gordon, Appl. Acoust. 10, 57--69 (1977)] have focused attention on human hearing in the 20--100 Hz range. New instruments are being developed and controlled clinical tests are planned with hearers and nonhearers in the Taos area.