The nuclear power plant had built the homes to house workers in the early 1980s and to an early form of Energy Star compliance, with an emphasis on being air-tight. Radon was trapped in these homes, workers set off the alarms, and the radon mitigation industry was born.
Just to add a little humanity here among all the numbers, I would have loved to have known my mother. I'm sure adopted children have similar thoughts, but I doubt there's anything quite the feeling of being given life during another's unwitting sacrifice. Would she have changed anything had she known the outcome? It occurred to me from a young age that I should try my best not to squander my opportunities in life.
Acoustics consultant here. Its too bad there's no mention of using a windscreen on the sound level meter, especially at 2 inch distance. It would make sense if the mesh performed best, while airflow was restricted nearly most if air rushing by the microphone element was contributing to the level measured, and not the noise of the fan itself.
You know how someone blowing in your ear makes more sound than when you blow in someone else's ear? The airflow itself can make sound from eddies and whatnot.
Most people don't put their ear next to a case fan to see if it's annoying or not. You experience its sound from several feet away, and the measurement should reflect that.
I think they mean the excess noise of a volume of air moving past your ear, which is due to the turbulence created while air is passing over your ear and not the soundwaves being transmitted by said volume of air.
Practically speaking no you wouldn't want to factor the turbulence generated at the microphone because the user of the computer wouldn't be hearing that.
Hey thanks. Yes, esoteric enough to keep it interesting day to day. I mostly work with architects and design engineers to coordinate quiet building systems and good interior acoustics--projects anywhere from K-12 to major performing arts centers to commercial offices, including some of your US offices...
On that point, I feel everyone's collective pain on the situation with open offices. I don't have the power to avoid them, so the best I can do is advocate for getting the signal-to-noise problem solved right.
One evening, I was sitting alone in the eating area of a very high end office, and noticed a whooshing sound coming from the top edge of the room. I thought it was maybe some air vent, but there was no wind outside. I stuck my phone camera up behind the front lip of a shelf and saw a set of speakers. They were playing something close to brown noise!
And, I learned about sound masking [1]. So, apparently there's two ends to be avoided, in the signal-to-noise problem!
1. Partitions around workspaces create a modest barrier effect, not so much realizable for your nearest neighbors but those more distant. No one installs partitions up to 48" or 52" but you have to at least break line of sight to the noisemaker to realize any improvement. This reduces signal.
2. Acoustically absorptive ceilings avoid the overhead reflection that would be the next cue to an occupant. The partition comes first, but this is second. Another signal reducer.
3. Background noise, whether a consistent HVAC system or sound masking system raises the noise floor of the environment. We have a pretty good sense of what level is acceptable to most people, but there will always be those with sensitivities. The noise is usually pink noise with some EQ to sound like HVAC air distribution. Unfortunately there has to be some treble in the noise signal to reduce the consonants of speech, which can be more annoying.
You won't make nearby co-workers inaudible, but the hope is that those 20 ft or so further will be less problematic. For inaudibility you have to get S/N to around -10 dB, that's a noise floor of 10 dB higher than the source, which is only realizable with walls at least to the ceiling.
A couple of decades back I was very involved with work that required paying attention to acoustics.
I remember building this room with walls lined with 1 foot thick Helmholtz resonators tuned to a range of frequencies. The same with portions of the ceiling. And, of course, there were broken-up and angled surfaces to help diffuse sound, avoid creating standing waves and stimulation of room modes. Back then I even wrote a bunch of software to run acoustics analysis and evaluate room characteristics based on a range of parameters, including construction materials, etc.
Since then I have always been very aware of acoustics in every environment. Restaurants are particularly horrendous. Nearly all of them seem to be reverberation chambers designed to destroy sound. Most would benefit greatly by deploying a few very simple tools to control sound and allow patrons to have conversations in a reasonable environment.
We use honeycomb panels in acoustics construction as means for high stiffness (low deflection) with the tradeoff of low mass. Often we laminated a thin layer of plywood to each side to improve the stress skin system. Orchestra shell towers are a common example of this, though we are also doing this for portable seating towers that need to reflect sound too. There are both wood pulp and aluminum versions commonly available in the US.
When I was a kid in the '80s, we had a Magnavox TV with built-in Pong. The game mode button was at the top of the side panel with the VHF and UHF knobs. Blue and Red controllers plugged into the back of the set, each with a rotary encoder and trigger.
I am an acoustics consultant who designs buildings with architects, then sees them through construction. Doors intended to isolate noisy rooms regularly underperform, whether due to manufacturing or installation problems. Lots of fingerpointing when we call it out on project sites, and having a camera show the weaknesses due to the perimeter gasketing, frame, door leaf, or wall construction surrounding the door would provide the necessary visual for contractors to see the problems we are pointing out.
I wonder how many building projects use and engage acoustic engineers (unless sound is specific to the use like for theatres or conference facilities)?
I had the "opportunity" as a patient in a very new hospital wing some 7 years ago for about 13 days. While I had a private room, the door was always open to the walkway, I guess as is normal to allow quick response by medical staff. But at one point I really felt overwhelmed by all the external noise that I could hear from the other rooms in the ward, nurse stations, and so on. I really felt that the hard surfaces and even the angular nature of the floor layout was conspiring against me - almost focussing noise into my room. I imagine given enough data you could show the poorer rest of patients prolonged their recovery period and hence increased bed occupancy and cost to the health system (important in a state run public hospital service that is predominant in Australia).
As such it would be nice to think hospitals, schools, offices would include thorough acoustic assessment to at least allow appropriate mitigation of noise during design (before having invoke more active measures like soft furnishings, etc).
My response is US-centric, but most hospital projects do have an acoustics consultant involved. Improvements have been made, but not nearly enough. Challenges include the need for sound absorption to be porous, but this is at odds with cleanability. Increased focus has been on patient room doors, which are increasingly sliders. They work well when they're closed, but the challenges include getting a good bottom seal when the threshold has to accommodate beds and equipment being rolled in and out. Hospital equipment manufacturers are also improving the sounds of their equipment, away from the cheap piezo beepers.
Schools very often have acoustics reviews, although more often in cities than rural areas. Classrooms in addition to auditoria, gyms and common areas. Standards exist for those too.
Office buildings are hit or miss. The developer may hire us for a base building review. Tenants' architects hire us as they design their workplaces. There's a lot of push and pull to find a balance of the modern open ceiling industrial aesthetic and glass conference rooms with reasonable acoustical goals.
Working in conference rooms, people far too often are concerned about the look ( big windows, natural light, great table ) and less concerned about acoustics than would be reasonable. In my experience, Architects think people just sit around the table, and chat.
I once had a brand new office upfit project with a "flagship room" that was a large flex space, (could be a board meeting, could be a hackathon). There were three sides of glass, a concrete floor and metal ceiling structure.
If you clapped in the room, it could be heard for 1.5 seconds as it bounced across all those surfaces before decaying.
My bosses were furious at the microphone quality, the installer was unhelpful and bailed on us. We hired a consultant to perform an evaluation and he told us that the room was awful, with lots of numbers ( figures for acoustic reverberation at different frequencies ) and told us of certain products that could help in those ranges.
It is a lot easier to design rooms with acoustic features than it is to retrofit them in terrible sounding rooms.
I think you're talking about a different problem, though that one could also be helped with the right tool.
After setting up the array, once could answer questions like "where is that darn squeak coming from!", and even characterize the undesirable noise, both spatially and spectrally. You could also measure how effective noise isolation materials are, but I don't see what the spatial information gets you.
However, if weaknesses due to "perimeter gasketing, frame, door leaf, or wall construction" result in some sort of localized noise, then a system like this would certainly pinpoint it.
Yes, this is in reference to noise passing through a door that is localizable. Typically we would play pink noise (broadband, equal energy per octave band) on one side and listen for "hotspots" on the quiet side. I would wonder about the precision of being able to tell in the image the contribution of the door frame from the perimeter gasketing.
Acoustic cameras like from Noiseless Acoustics are on the market though they seem to be marketed to industrial customers. There are similar mapping systems using a scanning mic like from Soft dB.
Ah! In that case yeah, this tech could possibly help. At least, I'd love to give it a shot! (I hope you don't mind an email from me later...)
It's sensitive enough to noise that I can pick up (and locate) the air vents in a room, even when the sound is at the threshold of hearing. Noise (pink and white), and even more so MLS (maximum length sequence) really "jumps out" (it's very obvious), well below my threshold of hearing.
There's so many interesting areas of research I've never had the time/money to fully investigate. I'd love to play with an "active" system, not just "passive", with a goal of experimentally finding modes of resonance of objects in a room.
I bet once can tell the relative contribution to noise of one physical object over another, but I don't know enough about construction to know if one would be able to separate the door frame from the perimeter gasketing. You do need line of sight for it to work. At the least, you'd have a way to quantify the sound leak, with numbers and reproducibility.
FWIW the Noiseless Acoustics camera costs ~$18k(!)
One problem is that a stolen iPhone is a >$1000 crime, in fact it passes the $950 threshold to be a felony in California[1]. Police don't have the resources to deal with every stolen phone.
When iPhones were new, my cousin was a police officer in a high school. Every time a kid stole an iPhone it was a felony on their juvenile record, and no one wanted that.
