Some people near the aircraft impacts didn't hear them

William Rodriguez's conspiracy theories begin with an assumption: that while on the B1 level of the north tower he heard and felt an explosion below him before flight 11 hit the building. He assumes that the next rumbling noise he heard, which he believes came from far above, was made by the aircraft impact. Of course, like most others in the building at first he didn't know that a plane had hit the building.

An examination of the vagaries of human hearing is beyond the scope of this paper. I do think it is interesting that humans are not very good at determining the direction and distance of low frequency sounds. Audio engineers use this fact to great effect.

For the record, I have no reason to doubt that Rodriguez did hear and feel an explosion from below before hearing a noise from above. One logical explanation for what Rodriguez experienced is that he did not hear the aircraft impact and that the noise from above was made by secondary fuel explosions, elevators crashing down, etc. We know that these secondary events happened. But is it possible that Rodriguez didn't hear flight 11's impact?

I think it is not only possible, but likely. I have been in the basements of some skyscrapers. The mechanical equipment there makes them noisy places. But what I find most interesting is that some people who were near the aircraft impacts did not hear them. Others couldn't tell whether the noise came from above or below. Some people who were familiar with the towers' mechanical equipment floors assumed that the explosions originated there. Many people, especially those who had survived the 1993 bombing, assumed that a bomb was responsible. Those were all understandable assumptions. Following are a variety of descriptions that may make Rodriguez question his certainty about what happened.

North Tower

91st floor
Mike McQuaid, the electrician installing fire alarms, was sure he knew what he was feeling: an exploding transformer, from a machine room somewhere below the 91st floor. Nothing else could rock the place with such power. Jim Dwyer and Kevin Flynn. 102 Minutes: The Untold Story of the Fight to Survive Inside the Twin Towers. Henry Holt and Company: New York. 2005.

81st floor, didn't hear impact.
Michael Wright: "All of a sudden there was this shift of an earthquake. People ask, "Did you hear a boom?" No, the way I can best describe it is that every joint in the building jolted...we all got knocked off balance...the flex caused the marble walls in the bathroom to crack...I opened the bathroom door, looked outside, and saw fire...The doorjamb had folded in on itself and sealed the door shut...There was a huge crack in the floor of the hallway that was about half a football field long, and the elevator bank by my office was completely blown out. If I'd walked over, I could have looked all the way down. Chunks of material that had been part of the wall were in flames all over the floor. Smoke was everywhere." ("What We Saw: The Events of September 11 in Words, Pictures, and Video. New York: Simon & Schuster, 2002. p. 72)

78th Floor
Schofield: My father had no idea what had happened. He and his co-workers were not terribly alarmed before I called. They knew something had happened, for they felt the building shake a bit. Source

77th Floor:
Sue Frederick: When the plane struck the building it felt exactly like an earthquake. The only advanced sound was a large windful swoosh. At first we had no idea if it was a bomb or the building had been struck. Source

72nd Floor
Frank Lombardi, Port Authority Chief Engineer
Lombardi was at his desk. He heard nothing, but felt the tower sway, and saw people in the hallway go airborne before they fell. His first thought was that New York was experiencing an earthquake.William Langewiesche. American Ground. New York: North Point Press, 2002. p.47

71st floor: “Heard a rumble”
Vincent Fiori was on the 71st floor of the first tower that was hit. “I’m sitting at my computer and I heard a rumble and my chair spun around,” he said. Most people weren’t sure what had happened. On the street, people gazed up at the gaping, smoking hole in the building, some holding handkerchiefs over their mouths, more curious than frightened. Source

60th floor: Didn't hear Impact
"Perez is still counting his blessings since he got out of the World Trade Center just minutes before it came tumbling down. An employee of Ahasi Bank, Perez was working on the 60th floor of Tower 1, when the first of two hijacked planes hit his building. "We didn't hear the impact," he said. "What we felt was it trembling. The trembling continued and the building actually started swaying." Source

55th floor: gigantic boom "right on top," violent shaking, then swaying.
ROBERT IDEISHI: Mr. Hayes went through the first few introductory slides of his presentation when suddenly we heard this extremely loud "boom". It sounded like a gigantic sonic boom was right on top of us. Then the building started to shake…violently!! I don't know how long the shaking lasted but it seemed like it was at least five seconds. Knowing I was the only other person from California, Mr. Hayes looked at me and said, "Feels like a big earthquake doesn't it?" I didn't know what it was but I said, "yeah" anyway. Then the building started to sway…A LOT! It seemed to sway once to our left and then once, WAY to the right. When it swayed right it felt, for an instant, that there was a possibility that the building could tip over. Source

50th Floor Elevator, with Demczur, didn’t know about explosion
George S. Phoeniz III: The elevator started moving. Suddenly it stopped and banged violently from side to side. The lights were still on. We pushed the emergency call button to call for help. As far as we were concerned, the only thing that happened was that the elevator had stopped.Source

40th floor
Yin Liang: At around 8:46 AM, when I am still reading and writing emails in front of my computer, I heard a low-pitched "Bom" noise, it's not very loud, then the floors starts moving, it swings back and forth slowly, like floating in the air, then the swing gradually stopped. Source

35th floor
Kemper Insurance executive Susan Doyle was in an colleague's 35th-floor office in the North Tower of the World Trade Center on Tuesday morning when the building began to shudder. The jolt was so strong that the tower "felt like it might fall over," she recalls. Her first instinct, in fact, was that it was an earthquake. But then, she and others peered out the windows and noticed that the rest of lower Manhattan looked normal. And that's when it dawned on them: "Whatever had happened had happened just to us. We all looked at one another and knew we needed to get out." Source

28th Floor: felt shaking before hearing. Didn’t hear explosion.
Julie Anderson, 33, manager of public affairs, was in her office on the 28th floor, talking with a co-worker, when they felt the building shake, then heard a "screechy sound," presumably of metal grinding. Source

8th Floor: Felt a couple of shudders
Richard P. Stearns: I was in a windowless sealed server room lab at the core of the 8th floor, and in all the din of the machines all I felt were a couple judders.

No fire alarms, no alarms of any kind (six months ago there had been a fire on the escalators and no alarms then either). Since construction was going on and large bangs were common and I worked on.

When I stepped out, the floor was empty (it was by now somewhere after 9am). I went to the lifts and they were not working, my heart started to race as I found the fire escape. It was filled with smoke and panicked people still trying to get out. Joining them we eventually made it into the atrium and onto the street outside. Source

At 8:48 a.m., Sept. 11, Capps was in a business meeting in a restaurant on the first floor of Tower 1 in the World Trade Center complex. He didn't hear an explosion, but when the chandelier above him began to shake, he was reminded of the earthquake he experienced in San Francisco eight years ago. Source

But also in a restaurant in the north tower’s ground floor was James Cutler:

1st Floor James Cutler, a 31-year-old insurance broker, was in the Akbar restaurant on the ground floor of the World Trade Center when he heard “boom, boom, boom,” he recalls. In seconds, the kitchen doors blew open, smoke and ash poured into the restaurant and the ceiling collapsed. Mr. Cutler didn’t know what had happened yet, but he found himself standing among bodies strewn across the floor. “It was mayhem,” he says. Source

South Tower

Brian Clark was on the 84th floor when flight 175 hit just below:
"It wasn't a huge explosion. It was something muffled, no flames, no smoke, but the room fell apart as the plane kind of torqued the building. Ceiling tiles fell from the ceiling, air conditioning ducts fell, door frames fell out of the wall. (Richard Bernstein. Out of the Blue. New York. Times Books, 2002. p. 222)

68th floor
Charles Caraher and Catherine Balkin: I started to leave a message and as I did so, the building jolted. ...I was trying to process what was happening around me. Once again I heard a “whoosh” surging through the ventilation ducts. This one was much, much more pronounced than the first one. It also sounded like large pieces of furniture were being moved across the floor above me.

62ndth Floor: Didn’t hear anything.
Daniel T. Duffy: I heard no sound - no crash, no explosion, no screams, but I felt that fortress of steel and glass wobble back and forth like it was a cheap card table, nearly knocking me off my feet. It felt for a moment as if the entire building would go toppling over onto Church Street. Source

53rd floor
Jack Alvo: I felt the impact of the explosion that I believed was at my feet. I heard the crashing glass around me as the building rocked. My hands began to shake and my knees buckled. I knew I could not stay where I was and I had to go lower. I made my way to the stairs, passing people along the way. I saw the horror and the fear in several faces as I went by them. I still believed the impact was at my feet and as I descended past floor 50 and floor 40 I was sure I was going to see disaster. Source

Middle floors, on impact of flight 175
I was not sure if there was another plane or a bomb and furthermore did not know if the fire and explosion was above or below me. All I did know was that It was getting very hot and I could smell the fire and see smoke coming up the stairwell. Source

44th Floor Sky Lobby
James Kazalis: As I took a few steps towards someone I recognized, some great force struck my building. It felt like the floor was being violently pushed under my feet. While falling to the floor, the steady repeating rhythm of time suddenly stopped. I instantly developed tunnel vision and my depth perception did not extend beyond twenty feet. My eyes focused on a nearby out-of-service elevator. The impact had created a shock wave through the entire building that forced dust at a high velocity from all four sides of the elevator doors to the inside of the lobby. I was now prone on the floor. Pandemonium erupted and filled the sky lobby. lobby. Source