A San Francisco audio salesman said he has refused to sell the loudspeaker -- similar to those used at Yankee Stadium and the Indy 500 to the scientists.
The planned monkey experiment "is kind of inhumane," charged Radley Hirsch, founder and owner of San Francisco Audio. Hirsch complained to People for the Ethical Treatment of Animals (PETA), an animal rights group in Norfolk, Va.
Mary Beth Sweetland, PETA's director of research, investigations and rescue, faxed a letter to UCSF Chancellor Dr. Haile Debas, asking him to intercede in the matter.
"According to Mr. Hirsch," Sweetland's letter said, "Fong and Cheung described experiments in which monkeys will be subjected to four-hour sessions of exposure to the loudspeakers, which deliver noise at a level exceeding that made by jet engines upon takeoff."
Sweetland repeated Hirsch's claim that one researcher had told him the 145-decibel speaker would be used to "create lesions in monkeys' ears."
The letter identified the researchers as Marshal Fong and Stephen Cheung.
Zach Hall, vice chancellor for research at UCSF, confirmed the plans for the experiments. "These are not experiments that we are in any sense ashamed of," Hall said.
The squirrel monkeys will be anesthetized, then exposed to "very high-frequency range" sounds in the experiments, Hall said.
"The animals, when they wake up, will have a hearing disability, one that's similar to one that millions of Americans have" -- namely, an inability to hear high-frequency sounds, he said.
"It's precisely the kind of high-frequency hearing loss you get from going to rock concerts or being near airplanes," Hall said. "Some 40 percent of Americans have high-frequency hearing loss. It may be worse for younger people because of their exposure to loud sound," principally high-volume music.
Hall confirmed that the animals' ears will suffer "lesions." Because of the high-frequency sounds, "sensory cells called hair cells -- the primary sensory cells in hearing pathways -- (will be) lost, die. ... It is a permanent loss," he said.
Hall said the experiments are funded by the university, and that the research has been "thoroughly reviewed and approved by the committee on animal research."
During the experiment, and on a separate occasion three months later, each of the six monkeys' brains will be surgically cut open and examined, said Hall, who is also a professor of neurophysiology and physiology at UCSF.
"It sounds awful that you're going to deafen animals by playing loud noise," Hall said. "But once you know that they're anesthetized, that they lose hearing only over a limited high-frequency range, and that their disability is similar to that suffered by millions of Americans, then the experiments ... sound much less drastic, much more reasonable and thoughtful."
Such research has practical benefits, Hall said.
"The research seeks to understand the changes that occur in the brain as a result of sensory deprivation (in this case, hearing loss)," he said, "with the hope that we can use what we learn to relieve the hearing loss caused by loud noise."
The experiments are scheduled to start at an undetermined time and are led by Cheung, a medical doctor in the UCSF department of otolaryngology, Hall said. Fong is an electronics technician.
Cheung could not be reached for comment.
Fong refused to discuss the issue in detail. "These people (the critics) are distorting the truth here," Fong said.
Hirsch said Fong originally contacted him Feb. 11. He said he didn't learn the purpose of the experiment for several weeks.
On learning the purpose of the experiment, he refused to sell Fong the speaker, Hirsch said.
"It all comes back to you," he said, explaining his philosophy of life. "If you're an evil person, bad things happen to you, and if you're a good person, nice things happen to you."