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Re: HUM_FORUM: Amazing! The HUM. I find others.....

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  • oldnickagain
    ... are ... produced at the ... etc. . ... keep a log ... coming from, ... perhaps? ... possible, it ... can analyse ... typical range ... I also figure it s
    Message 1 of 5 , Oct 3, 2004
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      --- In humforum@yahoogroups.com, Tobypaws2002@a... wrote:

      > all. That shows to me
      > 1) what a terrific din the modern urban life makes,
      > 2) how low frequency noise can travel on the wind or breeze : we
      are
      > several miles from the city-proper, where there is most noise being
      produced at the
      > docks, factories, power stations, sub stations, motorways, etc.,
      etc. .
      > Have you noticed if wind direction affects the volume? Could you
      keep a log
      > for a few weeks, with wind directions, and see where the wind is
      coming from,
      > when the noise is loudest?
      > Could you try to get hold of a D.A.T recorder? Could one be hired,
      perhaps?
      > Borrowed?
      > If you could get a recording,using the best quality microphones
      possible, it
      > would be so helpful. I have a programme on the computer that
      can analyse
      > sound frequencies within a recorded sound.
      > I have settled on a range of about 30 to 80 Hz, as being the
      typical range
      > of most annoying hums from noise sources, of which there are many.
      > R.M. England.

      I also figure it's city noise. I have not noticed a correlation
      between wind direction and the hum. I may check that out. I have not
      recorded it, but have "kept an eye (ear?) on it" and I think it
      depends on extraneous noise rather than wind direction. Wind is
      itself an extraneous noise of course! D'Oh!

      No need for a DAT! a computer is a perfectly good DAT, with a
      soundcard. I also have filtering and analysis stuff, and have done a
      fair bot of work like that in the past.

      Now a decent mic is a different story. In fact even a DAT may not
      suit, as it's aim is to measure Audio. This sound could easily be sub-
      sonic, or a range that gets down to subsonic and we hear only the
      sonic part, because I and many others report "feeling" it rather then
      hearing it.
    • oldnickagain
      ... are ... produced at the ... etc. . ... keep a log ... coming from, ... perhaps? ... possible, it ... can analyse ... typical range ... I also figure it s
      Message 2 of 5 , Oct 3, 2004
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        --- In humforum@yahoogroups.com, Tobypaws2002@a... wrote:

        > all. That shows to me
        > 1) what a terrific din the modern urban life makes,
        > 2) how low frequency noise can travel on the wind or breeze : we
        are
        > several miles from the city-proper, where there is most noise being
        produced at the
        > docks, factories, power stations, sub stations, motorways, etc.,
        etc. .
        > Have you noticed if wind direction affects the volume? Could you
        keep a log
        > for a few weeks, with wind directions, and see where the wind is
        coming from,
        > when the noise is loudest?
        > Could you try to get hold of a D.A.T recorder? Could one be hired,
        perhaps?
        > Borrowed?
        > If you could get a recording,using the best quality microphones
        possible, it
        > would be so helpful. I have a programme on the computer that
        can analyse
        > sound frequencies within a recorded sound.
        > I have settled on a range of about 30 to 80 Hz, as being the
        typical range
        > of most annoying hums from noise sources, of which there are many.
        > R.M. England.

        I also figure it's city noise. I have not noticed a correlation
        between wind direction and the hum. I may check that out. I have not
        recorded it, but have "kept an eye (ear?) on it" and I think it
        depends on extraneous noise rather than wind direction. Wind is
        itself an extraneous noise of course! D'Oh!

        No need for a DAT! a computer is a perfectly good DAT, with a
        soundcard. I also have filtering and analysis stuff, and have done a
        fair bot of work like that in the past.

        Now a decent mic is a different story. In fact even a DAT may not
        suit, as it's aim is to measure Audio. This sound could easily be sub-
        sonic, or a range that gets down to subsonic and we hear only the
        sonic part, because I and many others report "feeling" it rather then
        hearing it.
      • Tobypaws2002@aol.com
        In a message dated 04/10/2004 07:12:38 GMT Daylight Time, dropbear@dodo.com.au writes: Now a decent mic is a different story. In fact even a DAT may not suit,
        Message 3 of 5 , Oct 4, 2004
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          In a message dated 04/10/2004 07:12:38 GMT Daylight Time, dropbear@... writes:
          Now a decent mic is a different story. In fact even a DAT may not
          suit, as it's aim is to measure Audio. This sound could easily be sub-
          sonic, or a range that gets down to subsonic and we hear only the
          sonic part, because I and many others report "feeling" it rather then
          hearing it.
          Many thanks for your reply.
          I am mostly interested in the approximate range, 20 to 100Hz, as that is where I expect to find most annoying hums. As I understand it, most good microphones will cover from 20Hz upwards, so that's good enough for now.....let's see what is there in that range, I bet there is something....
          Thanks again, Keep in touch : your message was interesting.
          (By the way, moderator says we are each only supposed to write 3 messages a day.....just thought I'd mention that.....)(Personally I say the more messages, the merrier, but there you go...).
          Best Wishes,
          R.M.   England
        • oldnickagain
          ... Just OOI. A quote from a torist guide in our area. http://www.yetizone.com/australia/Bibbulmun/Track/Bibbulmun- Track.shtml It s about a walking track, so
          Message 4 of 5 , Oct 4, 2004
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            --- In humforum@yahoogroups.com, Tobypaws2002@a... wrote:

            Just OOI. A quote from a torist guide in our area.

            http://www.yetizone.com/australia/Bibbulmun/Track/Bibbulmun-
            Track.shtml

            It's about a walking track, so you could easily be talking 20-40
            miles over a couple of days. And that's one source only.

            My point here is not to argue ground or air etc, but simply to show
            that a sound can travel a long way, and all this hum could simply be,
            as you surmise, noise! <G>

            "The Worsley Alumina Conveyor is evident and the hum from it will be
            audible for the next day or so. Possum Springs is situated .... "

            > Many thanks for your reply.
            > I am mostly interested in the approximate range, 20 to 100Hz, as
            that is
            > where I expect to find most annoying hums. As I understand it, most
            good
            > microphones will cover from 20Hz upwards, so that's good enough
            for now.....let's
            > see what is there in that range, I bet there is something....

            hmmm....yes and no. I agree it's a start. It establishes that you are
            not imagining stuff! <G>

            I say all of this knowing I should get off my duff and _do_
            something. I was rather overwhelmed by reported previous failures by
            others.

            I dig up rusty memoriesm, leaned in the class and "in the field" many
            moons ago........

            If I preach to the knoweldgable, sorry. It may help someone. Let's
            know.

            I was amazed at the amount of tries that have been made to record
            this stuff, and the few successes. It may be tough. They may all be
            mad! It's happened before! <G>


            - the fact that this sound "comes from everywhere" indicates a very
            low frequency. But many people report hearing quite "high" sounds. My
            perception is around 65 Hz, with a beat. Low diesel. Some say idling
            diesel. Maybe they are "hearing" a lower portion. One other guy
            reported waiting "for the machine to finish the row" which indicates
            a higher perceived sound again. The synthetic sound that one poster
            said produced the most common "Yes" was quite high, but was made up
            of other sounds working together.

            - Speakers and mics all have a cutoff. More usually a rolloff, unless
            they are _very_ good. So a mic that "goes to 20Hz" would need to be
            able to show a pretty straight line to that point before it would be
            useful. Many mics are _designed_ to cut the lows to stop thumping and
            breath popping. Usually they quote the +-3dB point. But watch out for
            dips or resonances in the range near it. This is why that guy was
            building weird stuff from piezo bits with great big
            heavy "diaphragms", I would assume. Piezo goes down to 0Hz (DC), and
            the high mass, large sized diaphgragm would aid this by covering a
            more significant portion of the waveform.

            - As with my tests in the past, your test will only show you what you
            hear. This does not demonstrate the real nature of the noise,
            necessarily. As I said in another post, it leaves me knowing that I
            am not imagining things, but with no real idea of the source of the
            sound, or its true makeup.
            - What I "hear" could be made up of really loud sub-sonics
            modulating sonics, or the beat between two frequencies etc. It may be
            what my ears report from feeling a subsonic wave. Same with the mic.
            - mics, speakers and to a certain extent your ears will
            reproduce harmonics of every sound, and especially low sounds. So
            what you hear is not necessarily what you are getting.

            > Thanks again, Keep in touch : your message was interesting.
            > (By the way, moderator says we are each only supposed to write 3
            messages a
            > day.....just thought I'd mention that.....)(Personally I say the
            more
            > messages, the merrier, but there you go...).

            Ah. OK. Thanks. Well, I think I got a bit "merry" with my messages
            and posted at least two twice yesterday <G>. I am not sure how.
            Something to do with navigating using the back button in IE. I was
            not actually "merry" at the time<G> I will bear the 3-message limit
            in mind, on the same basis as you! <G>

            Tthe HUM, by the way is awful today, and was all last night. Luckily
            am chainsawing and driving machinery, and not sitting and trying to
            think in the shed. Last night I had the TV off-station as white
            noise, and two fan heaters running as fans. I could still hear it.
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