MTO's noise guidelines state that if a proposed highway project may result in >5dB or will make for a total noise increase over 65dB, MTO is to merely investigate mitigation (e.g. noise walls, berms) and determine 'technical and economic feasibility.' Basically, if they determine they can't construct it without difficulty or it's too damn expensive, they don't have to do anything, and can negotiate with a property owner over compensation.
Vibration, I can understand. But that these people are complaining over a 4.5dB increase in noise makes me laugh.
That's an excellent way of putting it. It's by analogy that Metrolinx must make their case. It doesn't help that they publish study samples that are preceded by provisos that pretty much debase what the samples *apparently* indicate. And then ML themselves group dB levels in "inconsequential" "somewhat significant" "significant" and "very significant" impact groups (my gist of terms they use, I'll paste in the actual text later). Even adding reference to the use of dB with "A" "B" or other weightings, and for pressure v. power ratios is still only as meaningful as other factors, such as *distance from source*, *height from source*, *geologically absorptive properties* etc. A quick analogy: Blaring music in sports auditorium v. a padded seat, acoustically damped and full of spectator listening hall.
That highway barrier comparison is an excellent one, because it's much more 'like for like'. And on that note, we all know how much quieter electric vehicles are than internal combustion ones. Sure, the big truck wheels are still going to whine, but that brings in another difference in 'noise' perception: The *nature* of the noise, the number of harsh, spiked, dissonant frequencies, for instance. Or as a listener might phrase it "loud but sweet" is easier to live with than "quiet but obnoxious".
Psychoacoustics is a specialty field in itself, there's even an area of medical/physics specialty beyond that, name escapes me at this moment, and incredibly, there's been little to no discussion about that.
A finger nail scratching on a blackboard doesn't have to be that loud to be obnoxious, if not intolerable. Again, the highway analogy takes all of that into consideration. (Edit: Excellent case in point: those small engined gasoline powered mopeds that make you want to swat them...or worse. Not that loud, would easily pass a muffler test, but ffffing irritating and obnoxious)
And of course, a factor almost all of us will relate to far more than the average affected listener: We love the sound of trains! Again, since none of the lines being discussed host any freight other than slow and temporally separated ones, and only occasionally, a whole segment of 'dissonant sound' can be eliminated from the area of concern, let alone health concerns of what the freight carried is.
Edit: To illustrate the 'height of sound source' factor: It's easy to notice when an airplane goes through a thick cloud how the sound (the higher frequencies are always absorbed much more readily) is often almost completely absorbed until the aircraft re-emerges, and you can hear it again. The same rate of absorption increases dramatically the closer the source and listener get to land, the more lush the vegetation, or disbursed the hard features (large rocks, etc) the more sound is absorbed and/or disbursed. Sound walls are often built of a zig-zag and absorptive nature (resin bound open fibres) to maximize both absorption and disbursement.
And another factor, train length, which makes an amazing difference:
https://www.youtube.com/watch?v=F-7Chrx-sX8
(Note that RER in Toronto will be travelling at a fraction of this speed, and be the square root of intensity for every time velocity is halved)
