Thomas Donnellan and Paul Kurtz of the Applied Research Lab said they were as horrified by the Sept. 11 tragedy as all Americans. While many people want to help, Donellan and Kurtz recognized that, as acoustic specialists, they had a skill that could be useful in the rescue effort.

So after making a few phone calls, the team of Donnellan, Anthony Atchley, Thomas Gabrielson and Matthew Poese received the word on Sept. 14 that they were being summoned.

On Sept. 15, they went to Ground Zero to help Pennsylvania Task Force 1, an Urban Search and Rescue (USAR) team headquartered in Harrisburg.

"Our job was to learn as much as we could about the types of acoustic and vibration devices that they had with them and the types of devices we could fabricate on site that could expand their capabilities," said Atchley, professor and head of the graduate program in acoustics. "We were also there to respond to whatever request we could for technical assistance. Foremost, however, our job was to in no way interfere with the search and rescue efforts."

Upon their arrival in New York, the four men had to assure their hotel security that they were not dangerous, which was an especially lengthy process with such heightened security measures in the city, they said.

Their first task was to create a small, battery-operated device capable of broadcasting very loud sounds and recording any response that could be lowered on a rope into an elevator shaft or large hole. They also had no electrical power available to them.

After a few hours, the team had built the device, but it was never deployed because the USAR team assigned to them had be reassigned to a new job. The rescue effort was extremely complex and changed continually.

"You have to keep in mind that the rescue effort is enormous," Donnellan said. "Sometimes a particular USAR task force would be searching for victims in the pile. Other times they would be assigned to search for victims in surrounding buildings. At yet other times, they would be assigned to help stabilize the pile structurally to make it safe for other teams to search."

The USAR teams work long hours and must be willing to sacrifice their lives in such threatening conditions, so the Penn State group had to be careful not to undermine their authority.

"We gained a greater respect for the USAR teams," said Gabrielson, senior research assistant in the research lab. "Second, we learned how important the makeup of our teams is. Fortunately, we all worked well together under difficult conditions and all worked well with the USAR team. Had one member of our team displayed the wrong attitude, we all would have lost credibility and been shut out."

The four specialists said they developed a good rapport with the New York workers.

"We were struck with how willing the police and rescuers were to help us," Poese said.

The specialists had taken a Nassau County Police patrol boat to the scene at 5:30 a.m. on Sept. 17. Once they got there, the Penn Staters took measurements and examined the current equipment so they could analyze possible ways to improve it.

"We learned that our USAR team was being assigned to areas where it was very unlikely to find survivors," Poese said.

The group had to stay optimistic, though, and continue with their efforts. Their biggest task was to record the background noise and vibrations on parts of the pile.

"Many people had told us our types of sensors would be worthless because of the loud noises and large vibrations made by heavy equipment in the area," Gabrielson said. "Our measurements showed that this speculation was simply wrong."

The Penn State team determined that if victims had been banging on a steel I-beam, their sensors would have picked it up. Then the problem would be getting to the victims, but the team did not detect any sounds of this kind and did not find any survivors.

"Of course we were disappointed that we did not get the chance to find survivors," Poese said. "If we could have gotten to the site sooner, perhaps it would have been different."

The specialists believe that everything that could have been done, though, was done.

"We feel we did the best we could given the situation," Donnellan said. "In light of the terrible tragedy that lay before us, we made valuable measurements that hold the potential to help if, God forbid, such a thing ever happens again."

The scene itself stirred emotions in the men, they said.

"The vision of Ground Zero is overwhelming," Atchley said. "Even having seen it first hand, one still has difficulty comprehending how two 110-story buildings could be reduced to such a relatively small pile of twisted metal and rubble. It was even more difficult to come to grips with the fact that we were treading on ground that concealed so many victims."

The specialists are unsure whether or not they will be called back to help again.