Hotel acoustics question

Of late, I’ve had the chance to measure the soundproofing abilities of the walls at perhaps two dozen hotels. The lodgings range in quality from “budget” to “upscale.” While we don’t have final results yet, the preliminary results seem to indicate that some “upscale” hotels with interior hallways do a slightly worse job of soundproofing than “moderate” hotels with exterior hallways. (By “interior hallways,” I mean that the entrances to each room are enclosed in a carpeted, covered hallway inside the hotel. Contrast this with exterior hallways, which are open to the elements on one side, and have concrete walkways.)

The same company owns all of the hotels, so while they hotels were built at different times, I’d expect there to be fewer variations in construction techniques and material quality than if they were all separately owned.

Our initial hypothesis is that sound waves in the halls of the upscale resorts simply bounce around from wall to wall, resulting in more noise, whereas some sound waves in the moderate resorts bounce off one wall and out into space. But I’d like to hear the opinions of any SDMB members with experince in acoustics to weigh in, too.

Thanks very much,


Hotels, Motels, hallways, and porches.
A hotel/motel with hallways have doors to access the rooms. These are the principal source of annoying sounds from other guests.
A motel/hotel with exterior covered walkways of porches (which do not meet the definition of hallways :rolleyes: ) have the room doors opening to the outsice so that sounds from adjacent rooms are more isolated than in the prior case.

You don’t describe your methodology, so I don’t know how you measured this objectively. That would be of interest.

There are many variables at play but I will address the two that come off the top of my head.

You are more or less correct about the idea that "sound waves in the halls of the upscale resorts simply bounce around from wall to wall, resulting in more noise, whereas some sound waves in the moderate resorts bounce off one wall and out into space. " In a closed space you will have resonant frequencies such that a noise of that frequency will result in a louder sound than other sounds at other frequencies generated with the same amount of energy. The great outdoors for all practical purposes does not have much in the way of resonant frequencies. So a hallway will make at least some sounds louder.

However, sounds from outside can be rather loud, regardless of resonance. One thing you did not take into account is the insulation to the outside, which is generally heavier than interior insulation. For example, next time you’re in a hotel with an interior hall, look at the bottom of your door. There will be a crack big enough for a mouse to crawl through. There is also no seal around the sides or top of the door. In a door to the outside, there will be weather stripping and no cracks. The same is probably true of the construction of the walls. Exterior walls would be thicker, made of heavier material (opposed to studs and drywall on the interior walls), and better insulated (as insulation against the elements saves energy and therefore money, but insulation against sound results in mere customer satisfaction).

Ah, that’s a good explanation, CookingWithGas. We did notice the gaps at the bottom of the interior doors. Some has as much as 0.75" of space, which seemed a bit excessive to me. I’m told that’s to help with air circulation, but I’m not sure that 0.75" is required for a hotel room that averages maybe 300 to 400 square feet.

As for the testing methodology, it involved a digital sound meter and a CD of The Who’s Greatest Hits. Okay, it was a bit more complicated that that, but those were the tools. I didn’t mention it, but we didn’t have the cooperation of the hotels when we did the test, so bringing in a bunch of test equipment wasn’t an option.


Sounds like too much fun.

Did you test room-to-room sound penetration, or just hallway-to-room penetration? One thing I don’t know is whether the hallway characterstics affect room-to-room penetration, although I imagine they would; the offending room door would probably act as a sound board and project into the hallway, resonating, therefore into the defending room door.

I would’ve selected Won’t Get Fooled Again as a good sample with a range of frequencies, dynamic ranges, and sustained ass-kicking to exercise resonances.

We initially tested both room-to-room and hallway-to-room, but switched to hallway-to-room when those first tests showed that was the weak link in the soundproofing chain. (It may have helped that there are typically two interior doors between connecting rooms.)

To do the tests, we played Baba O’Riley, adjusting the volume of the CD player until it read 70 db on the digital sound meter when the vocals kicked in. The distance between the two devices during this setup phase was 5 feet.

Then we took the CD player outside the room, and re-played the song (same distance from the door, same distance off the ground each time). We placed the sound meter on the closest pillow of the bed closest to the room’s door, and measured the sound reading at the same point in the song. We repeated the test a couple of times for consistency, but all of the results I saw were within +/- 2 db for the same room.

The best-performing rooms measured an interior sound level of less than 50 db off that 70 db source, while the worst were in the 64 to 65 range. While I know nothing about acoustics, I’m guessing that’s a significant variation, no?


It’s quite significant. The decibel scale is logarithmic: a 60 decibel sound is actually 10 times louder than a 50 decibel sound.

I don’t know what would be considered “significant” from a statistical standpoint but by the normal English use of the word, yes a hotel customer would easily be able to tell the difference.

Yes but the reason it’s logarithmic is to scale it to human perception. That is, a typical decibel reference will show a whisper at 20 dB and normal conversation at 60 dB. Most people would not subjectively say that normal conversation is 10,000 times louder than a whisper.