You tube (shunt) lorry driver keeps his HGV licence
in [UK Drivers]
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From: Albert T Cone on 28 May 2010 05:02 GT failed to quote properly: > " > So what's the frequency response of that "low quality, low > sensitivity" microphone? How does it corrspond to the frequencies > being emitted from (a) the scraping of the car (b) the engine noise? > " > > The frequency response of mobile phone mics are typically between 300 hertz > and 3,400 hertz, which is somewhere between the high pitched squeel of tyres > on tarmac and the low gritty noise of a large diesel engine. Despite the > noises being outwith the phone's sensitive response range, the phone would > picked up both noises with equal sensitivity. A lorry engine at motorway speeds will be running at what, 1000rpm? so that's about 16Hz. Assuming that it's an 8 cyl engine, that gives a power stroke freq of 32Hz. The majority of the sound produced by an engine is contained within the first four harmonics of the fundamental, so there won't be much over 150Hz, and less above 300Hz. The noise of tyres being pushed along a wet road is quite broad-band; something akin to pink noise, and there is certainly a significant component within the range used by human speech. In other words, it's very likely that the microphone will be more sensitive to the tyre noise than to the engine noise. Futhermore, the drivers cab is attached to the same frame as the engine, so engine noise and vibration will be conducted into the cabin - listening externally doesn't tell you anything quantifiable about the relative noise levels inside the cabin.
From: boltar2003 on 28 May 2010 05:13 On Thu, 27 May 2010 18:31:26 +0100 Dave <d(a)btinternet.com> wrote: >Yes...that would be nice, like the woman in the Vauxhall Zafira a week >or so ago who, as she moved in front of my truck from lane 2 promptly >jumped on the brakes because she wanted the exit immediately on my >left. She crossed the hatchings with feet to spare before the crash >barrier. I did something similar to that many many years ago when I was a wet behind the ears 21 year old. I missed the sign for the M6 turnoff on the northbound M1, just spotted the slip road at the last second and swerved across the inside lane in front of a trucker braking while I did so. He wasn't best pleased. It makes me grimace whenever I think about it now. B2003
From: boltar2003 on 28 May 2010 05:26 On Fri, 28 May 2010 10:02:40 +0100 Albert T Cone <a.k.kirby(a)durham.ac.uk> wrote: >In other words, it's very likely that the microphone will be more >sensitive to the tyre noise than to the engine noise. As will the human ear. B2003
From: GT on 28 May 2010 06:18 "Brimstone" <brimstone(a)hotmail.com> wrote in message news:1uqdnR-suoyRPWPWnZ2dnUVZ7oydnZ2d(a)bt.com... > "GT" <a(a)b.c> wrote in message > news:4bfe95d4$0$10334$c3e8da3(a)news.astraweb.com... >> "Brimstone" <brimstone(a)hotmail.com> wrote in message >> news:3fCdnY5Pq7q-D2PWnZ2dnUVZ8hGdnZ2d(a)bt.com... >>> "GT" <a(a)b.c> wrote in message >>> news:4bfe7464$0$10292$c3e8da3(a)news.astraweb.com... >>>> "Man at B&Q" <manatbandq(a)hotmail.com> wrote in message >>>> news:087a203b-560c-483c-90ff-9097c0a7d9f4(a)11g2000prv.googlegroups.com... >>>> On May 27, 11:30 am, "GT" <a...(a)b.c> wrote: >>>>> "Brimstone" <brimst...(a)hotmail.com> wrote in message >>>>> >>>>> news:s-mdnSZ1j58V1GPWnZ2dnUVZ8nWdnZ2d(a)bt.com... >>>>> >>>>> > <boltar2...(a)boltar.world> wrote in message >>>>> >news:htldfr$6gk$1(a)speranza.aioe.org... >>>>> >> On Thu, 27 May 2010 10:09:10 +0100 >>>>> >> "Brimstone" <brimst...(a)hotmail.com> wrote: >>>>> >>>> Well mine has about 350 but thats beside the point. The noise of >>>>> >>>> hitting >>>>> >>>> the >>>>> >>>> cone and the scraping sound would have been a giveaway if I >>>>> >>>> hadn't seen >>>>> >>>> it >>>>> >>>> already (cone knocked over by another vehicle in roadworks , >>>>> >>>> going to >>>>> >>>> fast >>>>> >>>> to >>>>> >>>> swerve , not an interesting tale). >>>>> >>>>> >>>What if you hadn't seen it and the collision was so gentle that >>>>> >>>there was >>>>> >>>no >>>>> >>>noise transmitted to you? >>>>> >>>>> >> Then I wouldn't have heard the initial bang. But I'd still have >>>>> >> heard the >>>>> >> scraping sound coming from under the car. >>>>> >>>>> > How do you know beyond all reasonable doubt that you would have >>>>> > heard it? >>>>> >>>>> Because it is audible on the video clip which is recorded on a low >>>>> quality, >>>>> low sensitivity microphone >>>> >>>> MBQ failed to indent his post: >>>> " >>>> So what's the frequency response of that "low quality, low >>>> sensitivity" microphone? How does it corrspond to the frequencies >>>> being emitted from (a) the scraping of the car (b) the engine noise? >>>> " >>>> >>>> The frequency response of mobile phone mics are typically between 300 >>>> hertz and 3,400 hertz, which is somewhere between the high pitched >>>> squeel of tyres on tarmac and the low gritty noise of a large diesel >>>> engine. Despite the noises being outwith the phone's sensitive response >>>> range, the phone would picked up both noises with equal sensitivity. >>>> >>> The only thing audible in the clip is a possible bit of wind noise, some >>> muffled sounds from the interior of the observer's car and the comment >>> from one of the occupants. >>> >>> What do you think can be heard? >> >> Wind noise at the start, until he closes his window, then the tyres >> screeching can be best heard between 9 and 11 seconds through that clip >> (through the glass as we previously established). > If what you say is correct, why can't we hear the car tyres screeching > with the window open? You answered that already the mic picks up nothing but wind noise.
From: GT on 28 May 2010 06:19
"Man at B&Q" <manatbandq(a)hotmail.com> wrote in message news:99b614b8-785b-4f74-9200-614efeaa281b(a)v37g2000vbv.googlegroups.com... On May 27, 4:39 pm, "Brimstone" <brimst...(a)hotmail.com> wrote: > "GT" <a...(a)b.c> wrote in message > > news:4bfe7464$0$10292$c3e8da3(a)news.astraweb.com... > > > "Man at B&Q" <manatba...(a)hotmail.com> wrote in message > >news:087a203b-560c-483c-90ff-9097c0a7d9f4(a)11g2000prv.googlegroups.com... > > On May 27, 11:30 am, "GT" <a...(a)b.c> wrote: > >> "Brimstone" <brimst...(a)hotmail.com> wrote in message > > >>news:s-mdnSZ1j58V1GPWnZ2dnUVZ8nWdnZ2d(a)bt.com... > > >> > <boltar2...(a)boltar.world> wrote in message > >> >news:htldfr$6gk$1(a)speranza.aioe.org... > >> >> On Thu, 27 May 2010 10:09:10 +0100 > >> >> "Brimstone" <brimst...(a)hotmail.com> wrote: > >> >>>> Well mine has about 350 but thats beside the point. The noise of > >> >>>> hitting > >> >>>> the > >> >>>> cone and the scraping sound would have been a giveaway if I hadn't > >> >>>> seen > >> >>>> it > >> >>>> already (cone knocked over by another vehicle in roadworks , going > >> >>>> to > >> >>>> fast > >> >>>> to > >> >>>> swerve , not an interesting tale). > > >> >>>What if you hadn't seen it and the collision was so gentle that > >> >>>there > >> >>>was > >> >>>no > >> >>>noise transmitted to you? > > >> >> Then I wouldn't have heard the initial bang. But I'd still have > >> >> heard > >> >> the > >> >> scraping sound coming from under the car. > > >> > How do you know beyond all reasonable doubt that you would have heard > >> > it? > > >> Because it is audible on the video clip which is recorded on a low > >> quality, > >> low sensitivity microphone > > > MBQ failed to indent his post: > > " > > So what's the frequency response of that "low quality, low > > sensitivity" microphone? How does it corrspond to the frequencies > > being emitted from (a) the scraping of the car (b) the engine noise? > > " > > > The frequency response of mobile phone mics are typically between 300 > > hertz and 3,400 hertz, which is somewhere between the high pitched > > squeel > > of tyres on tarmac and the low gritty noise of a large diesel engine. > > Despite the noises being outwith the phone's sensitive response range, > > the > > phone would picked up both noises with equal sensitivity. > > The only thing audible in the clip is a possible bit of wind noise, some > muffled sounds from the interior of the observer's car and the comment > from > one of the occupants. Correct, and, not exactly a phorensic investigation but, if you watch carefully, and pause it at the right spot you can see the silhouette of the drivers head and deduce that the car is *not* in his line of site, due to the height of the windscreen. You can also see the car headlights running along the central barrier. Another clue to the truck driver that something is wrong - lights normally point forward on motorways. |