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RE: HUM_FORUM: Re: Hum Tones

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  • Geoff Wood
    ... Probably unrelated. ... Well that would be truly incredible, because telephones have an incredibly restricted bandwidth, 400Hz-4KHz = no bass response at
    Message 1 of 14 , Feb 5, 2009
      > -----Original Message-----
      > From: humforum@yahoogroups.com [mailto:humforum@yahoogroups.com] On
      > Behalf Of coatesmargaret


      >I suspect
      > anyway that it is a modulation of a lower frequency, as tests done
      > 40kms from here found
      > sounds between 10 and 12.5 Hz at 38 dBs.


      Probably unrelated.

      >The person in whose house
      > those tests were
      > done, claimed to hear my hum over the telephone and commented how loud
      > it was. He
      > hummed the sound he heard which matched mine.

      Well that would be truly incredible, because telephones have an incredibly
      restricted bandwidth, 400Hz-4KHz = no bass response at all ! Best he could
      hum would be a similar note, but several octaves higher.

      >
      > At times the musical note of my hum changes - I have heard C, G#, F.

      Mine is always a similar frequency - between 54 and 58Hz. Some people have
      75 or 85 Hz.

      Mine is sometimes constant, sometimes pulsing ( 5 second on/off), and
      sometimes modulated (tremolo with maybe 50% depth) at around 0.5Hz.
      Sometimes it is there continuously for hours ( usually evening if I'm
      tired), and other times it will suddenly start then stop after a few tens of
      seconds ( I have a similar mid-freq tinnitus tone that does that very
      occasionally). I also have very high freq tinnitus almost continuously in
      my left ear - not a pure tone like the other 'mid' one, but like a filds of
      cicadas on a hot sunny day ;-(

      geoff
    • Tom Becker
      ... he heard which matched mine. If the Hum he heard were from your telephone instrument microphone, it would need to have been above about 300Hz, the low end
      Message 2 of 14 , Feb 5, 2009
        > ... claimed to hear my hum over the telephone... He hummed the sound
        he heard which matched mine.

        If the Hum he heard were from your telephone instrument microphone, it
        would need to have been above about 300Hz, the low end of the classic
        telephone voice channel passband. The Hums most reported here are on
        the order of 40-70Hz; the powerline frequency in Australia is 50Hz so
        frequencies on that order are normally greatly attenuated by the
        telephone system because that frequency and its first few harmonics are
        so pervasive they would otherwise dominate every wired conversation. It
        is very unlikely that the gentlemen could hear your Hum via the
        telephone instrument.

        A telephone wiring problem called a ground fault most frequently
        produces a hum on the phone line; ground faults are often heard after
        rain which dampens wiring or, often, which wets an ant's nest in a
        telephone wiring closet or "pedestal" anywhere between the telephone and
        the phone company facility to which it connects. Hum harmonics produced
        by a ground fault can frequently be heard at the other end - not the
        fundamental frequency, which is attenuated, but any of many harmonics.

        I suspect you both were hearing some multiple of the powerline
        frequency in that call, not your Hum.


        Tom
      • Geoff Wood
        ... Correction. The cicadas are in my RIGHT ear, pretty much always, but usually strongest directly after work. I get Hum in my left , and sometimes both ears.
        Message 3 of 14 , Feb 5, 2009
          > -----Original Message-----
          > From: humforum@yahoogroups.com [mailto:humforum@yahoogroups.com] On
          > Behalf Of Geoff Wood
          > I also have very high freq tinnitus almost continuously
          > in my left ear - not a pure tone like the other 'mid' one, but like a
          > filds of cicadas on a hot sunny day ;-(

          Correction. The cicadas are in my RIGHT ear, pretty much always, but usually
          strongest directly after work.

          I get Hum in my left , and sometimes both ears. Not always ( now that my
          stress is lower - it was almost 100% for some years a while back), but when
          it is 'on' it is most strong (or noticeable) in the evenings, especially
          when trying to get to sleep.

          I get a very short mid-freq tinnitus sometimes in either or both ears
          (around 3KHz).

          I get blockages (and resultant bass-boost) in both , but more often right
          ear. Usually as a result of head-cold or sinus condition.

          geoff
        • Geoff Wood
          ... The reason telephones have that restricted bandwidth is that 400Hz-4KHz is the minimum range of frequencies required to purvey speech sufficiently
          Message 4 of 14 , Feb 5, 2009
            > -----Original Message-----
            > From: humforum@yahoogroups.com [mailto:humforum@yahoogroups.com] On
            > Behalf Of Tom Becker


            > The Hums most reported here are on
            > the order of 40-70Hz; the powerline frequency in Australia is 50Hz so
            > frequencies on that order are normally greatly attenuated by the
            > telephone system because that frequency and its first few harmonics are
            > so pervasive they would otherwise dominate every wired conversation.

            The reason telephones have that restricted bandwidth is that 400Hz-4KHz is
            the minimum range of frequencies required to purvey speech sufficiently
            intelligibly. Wider bandwidths are possible (broadcast quality lines, etc),
            but reduce the capacity of the telephone transmission network, be it digital
            or the old FDM systems. Mains freq interference is a secondary factor.
            Because the telephone line are ( should be !) 'balanced' the effect is small
            - interference effects both 'legs' equally, and cancels itself out.

            > A telephone wiring problem called a ground fault most frequently
            > produces a hum on the phone line; ground faults are often heard after
            > rain which dampens wiring or, often, which wets an ant's nest in a
            > telephone wiring closet or "pedestal" anywhere between the telephone
            > and
            > the phone company facility to which it connects. Hum harmonics
            > produced
            > by a ground fault can frequently be heard at the other end - not the
            > fundamental frequency, which is attenuated, but any of many harmonics.
            >
            > I suspect you both were hearing some multiple of the powerline
            > frequency in that call, not your Hum.

            Agreed, especially if the gent had a modern 'electronic' phone, or wireless
            phone. Possibly even local mains hum induced or by poor power supply
            filtering in an electronic phone.

            geoff
          • Tom Becker
            ... Geoff, although immaterial to the thread, I m sure you mean to be technically accurate. Broadcast loops came about long after the wired telephone systems
            Message 5 of 14 , Feb 5, 2009
              > ... Mains freq interference is a secondary factor.

              Geoff, although immaterial to the thread, I'm sure you mean to be
              technically accurate.

              Broadcast loops came about long after the wired telephone systems were
              widely installed - in fact, it was not until the mid-1950s that
              broadcast audio required the 50Hz-15kHz bandwidth that is called
              "broadcast quality" - when FM radio licensing began. Prior to that,
              broadcasting was exclusively AM, which had a cutoff of 5kHz. To this
              day, except for short runs, wired 50Hz-15kHz loops require amplified
              equalization to meet that specification.

              The science of voice intelligence bandwidth was also a result of the
              need to multiplex several telephone voice channels into one coaxial
              cable and, later, microwave links.

              Telephone lines were not twisted pairs as they are today; they were two
              parallel wires, strung between glass insulators on pole crossarms; the
              wires' positions were exchanged at regular intervals, but were not
              "balanced" as we know the concept today.

              The principal reason for the low-frequency cutoff of telephone loops -
              long before twisted pairs, frequency-division multiplexing and FM
              broadcasting - was powerline hum suppression.


              Tom
            • Geoff Wood
              ... Exactly. But not entirely immaterial. ... Sure, but broadcast standard telephone ccts are merely a side-issue. But I ll need to correct my telephone
              Message 6 of 14 , Feb 5, 2009
                > -----Original Message-----
                > From: humforum@yahoogroups.com [mailto:humforum@yahoogroups.com] On
                > Behalf Of Tom Becker
                >
                > > ... Mains freq interference is a secondary factor.
                >
                > Geoff, although immaterial to the thread, I'm sure you mean to be
                > technically accurate.

                Exactly. But not entirely immaterial.

                > Broadcast loops came about long after the wired telephone systems were
                > widely installed - in fact, it was not until the mid-1950s that
                > broadcast audio required the 50Hz-15kHz bandwidth that is called
                > "broadcast quality" - when FM radio licensing began. Prior to that,
                > broadcasting was exclusively AM, which had a cutoff of 5kHz. To this
                > day, except for short runs, wired 50Hz-15kHz loops require amplified
                > equalization to meet that specification.

                Sure, but 'broadcast standard' telephone ccts are merely a side-issue. But
                I'll need to correct my telephone engineering tutors then , if they are
                still alive, on the reason for the standard telephone channel bandwidth !
                In the days of aerial wires, the carbon granule telephone 'transmitter'
                (microphone element) had little or no response to low frequencies, not to
                the rocking armature 'receivers' ( speakers).

                >
                > The science of voice intelligence bandwidth was also a result of the
                > need to multiplex several telephone voice channels into one coaxial
                > cable and, later, microwave links.

                It's not complicated enough to be a 'science' really. A minimum comfortable
                bandwidth requirement for intelligibility is the over-riding constraint was
                decided to be what is is, to fit as many channels as possible into a carrier
                system, be it digital or analogue FDM, whatever carrier frequency, and
                whatever the transmission medium be is overhead wires, coaxial cable,
                microwave, radio, or optical fibre.

                > Telephone lines were not twisted pairs as they are today; they were two
                > parallel wires, strung between glass insulators on pole crossarms; the
                > wires' positions were exchanged at regular intervals, but were not
                > "balanced" as we know the concept today.

                Well 'balancing' relates to the terminating arrangements, and the aerial
                transposition you mention (and well as twist in cable pairs) were/are
                exactly for the purpose of common-mode noise cancellation.


                > The principal reason for the low-frequency cutoff of telephone loops -
                > long before twisted pairs, frequency-division multiplexing and FM
                > broadcasting - was powerline hum suppression.

                I don't remember old passive telephones having explicit low and high-pass
                filtering - the bandwidth aspect of that era being inherent to the maximum
                capability of the telephone itself, and was further restricted if/when
                transformers, hybrids, and equalisers were introduced impassive ccts. In
                more modern ccts with active amplifiers, ceratinly the bandwidth must be
                deliberately controlled.

                The voice energy below several hundred hertz carries no intelligence, but
                lots of power, and the higher frequencies requiring to be filtered ( at the
                multiplexing equipment end) to restrict the modulation sideband width in FDM
                and prevent aliasing in digital.

                But the crux of all this is that it is certainly impossible for a 'Hum'
                frequency to be heard over anything but a 'broadcast-quality' telephone cct.
                And most peoples' Hums are pretty much pure fundamental frequencies, not
                containing large amounts of harmonics , which if sufficiently high frequency
                could be heard and mentally translated back down to the fundamental.

                Also a real hum at the one end *could* overload the microphone or
                electronics, and generate harmonics that could be passed. This would need to
                be either a significant level, or a very poor (distorted) microphone and/or
                handset electronics.

                geoff
              • Graeme Zimmer
                Tom, ... In the USA perhaps, but not in Australia or Europe. Although the stations were on 10 KHz channeling, the audio was allowed to extend to 15 KHz,
                Message 7 of 14 , Feb 5, 2009
                  Tom,

                  > Prior to that, broadcasting was exclusively AM, which had a cutoff of
                  > 5kHz.

                  In the USA perhaps, but not in Australia or Europe.

                  Although the stations were on 10 KHz channeling, the audio was allowed to
                  extend to 15 KHz, especially with ABC stations. Wideband AM tuners even
                  required a 10 KHz "whistle filter" to remove the inter-carrier hetrodynes.

                  Since 9 KHz channelling arrived, the stations have reduced audio B/W to 12
                  KHz (if memory serves).
                  Of course cheap radios designed for the USA market limit the B/W further.

                  Regards .............. Zim
                • coatesmargaret
                  Well it seems the other hum hearer couldn t have been hearing my hum over the telephone. Thanks for clarifying. In that case he was humming the sound he
                  Message 8 of 14 , Feb 8, 2009
                    Well it seems the other hum hearer couldn't have been hearing my hum over the
                    telephone. Thanks for clarifying. In that case he was humming the sound he heard in his
                    own house though having only the human voice to reproduce it, it would have been a
                    higher modulation. I do find that any musical note if it's loud enough, whether it's E1 or
                    E5 masks the hum.

                    But the point I was making still applies. We both heard a hum of the same pitch, though
                    40 kms apart.

                    Maggie

                    --- In humforum@yahoogroups.com, "Geoff Wood" <geoff@...> wrote:
                    >
                    >
                    >
                    > > -----Original Message-----
                    > > From: humforum@yahoogroups.com [mailto:humforum@yahoogroups.com] On
                    > > Behalf Of coatesmargaret
                    >
                    >
                    > >I suspect
                    > > anyway that it is a modulation of a lower frequency, as tests done
                    > > 40kms from here found
                    > > sounds between 10 and 12.5 Hz at 38 dBs.
                    >
                    >
                    > Probably unrelated.
                    >
                    > >The person in whose house
                    > > those tests were
                    > > done, claimed to hear my hum over the telephone and commented how loud
                    > > it was. He
                    > > hummed the sound he heard which matched mine.
                    >
                    > Well that would be truly incredible, because telephones have an incredibly
                    > restricted bandwidth, 400Hz-4KHz = no bass response at all ! Best he could
                    > hum would be a similar note, but several octaves higher.
                    >
                    > >
                    > > At times the musical note of my hum changes - I have heard C, G#, F.
                    >
                    > Mine is always a similar frequency - between 54 and 58Hz. Some people have
                    > 75 or 85 Hz.
                    >
                    > Mine is sometimes constant, sometimes pulsing ( 5 second on/off), and
                    > sometimes modulated (tremolo with maybe 50% depth) at around 0.5Hz.
                    > Sometimes it is there continuously for hours ( usually evening if I'm
                    > tired), and other times it will suddenly start then stop after a few tens of
                    > seconds ( I have a similar mid-freq tinnitus tone that does that very
                    > occasionally). I also have very high freq tinnitus almost continuously in
                    > my left ear - not a pure tone like the other 'mid' one, but like a filds of
                    > cicadas on a hot sunny day ;-(
                    >
                    > geoff
                    >
                  • Geoff Wood
                    ... But others nearby didn t....? geoff
                    Message 9 of 14 , Feb 8, 2009
                      coatesmargaret wrote:
                      > Well it seems the other hum hearer couldn't have been hearing my hum
                      > over the
                      > telephone. Thanks for clarifying. In that case he was humming the
                      > sound he heard in his
                      > own house though having only the human voice to reproduce it, it
                      > would have been a
                      > higher modulation. I do find that any musical note if it's loud
                      > enough, whether it's E1 or
                      > E5 masks the hum.
                      >
                      > But the point I was making still applies. We both heard a hum of the
                      > same pitch, though 40 kms apart.

                      But others nearby didn't....?

                      geoff
                    • coatesmargaret
                      But the point I was making still applies. We both heard a hum of the same pitch, though 40 kms apart. Maggie ... I didn t ask the other hum hearer about
                      Message 10 of 14 , Feb 10, 2009
                        But the point I was making still applies. We both heard a hum of the
                        same pitch, though 40 kms apart. Maggie

                        > But others nearby didn't....?
                        > >
                        > geoff

                        I didn't ask the other hum hearer about neighbours hearing it Geoff, but in the last couple
                        of years I have spoken freely about the hum and have found 18 or 19 other people who
                        hear a hum with a similar profile to what I hear. Three of those were neighbours. For two
                        of them it was quieter than what I heard, but the same pitch.

                        I gather you don't think that constitutes either proof or likelihood of the hum having an
                        external cause, as I note several people on this forum have already mentioned others have
                        heard their hum. So are you saying that you believe the hum ALWAYS has an internal
                        origin?

                        The consultant I referred to earlier, who was employed by the local council, used a C
                        weighted meter to measure the hum. Hence the reading of 10 to 12.5 Hz at 38dBs was
                        most likely accurate. An A weighted meter doesn't measure sound as low as that.

                        Geoff, you said in another message:
                        >Hum does sounds incredibly realistically ¡external¢, but isn¢t necessarily so, otherwise I
                        >would be hearing it in BOTH ears now, not just one.

                        Hearing the hum in only one ear, more often the left, according to early messages in this
                        forum, is one of the signs of the classical hum.

                        Regards Maggie


                        --- In humforum@yahoogroups.com, "Geoff Wood" <geoff@...> wrote:

                        > > But the point I was making still applies. We both heard a hum of the
                        > > same pitch, though 40 kms apart. Maggie
                        >
                        > But others nearby didn't....?
                        >
                        > geoff
                        >
                      • Geoff Wood
                        ... Same pitch, or similar pitch ? Most people suffering from hum hear a similar pitch, within a few notes . But some extend upwards to 75Hz or so - around
                        Message 11 of 14 , Feb 10, 2009
                          coatesmargaret wrote:

                          > I didn't ask the other hum hearer about neighbours hearing it Geoff,
                          > but in the last couple
                          > of years I have spoken freely about the hum and have found 18 or 19
                          > other people who
                          > hear a hum with a similar profile to what I hear. Three of those were
                          > neighbours. For two
                          > of them it was quieter than what I heard, but the same pitch.

                          Same pitch, or similar pitch ? Most people suffering from hum hear a
                          similar pitch, within a few 'notes'. But some extend upwards to 75Hz or so -
                          around half an octave higher than the average.


                          > I gather you don't think that constitutes either proof or likelihood
                          > of the hum having an
                          > external cause, as I note several people on this forum have already
                          > mentioned others have
                          > heard their hum. So are you saying that you believe the hum ALWAYS
                          > has an internal
                          > origin?

                          No, I've stated clearly that there are many external sources of hum. I can
                          identify at least 3 in my house pretty much all the time. These are local
                          magnified but resonant modes in remote locations in the house. It is The
                          Hum, the one that cannot be heard by everybody and cannot be measured or
                          recorded, that I think is internally generated.

                          Some others may hear a hum, but one needs to be a bit more objective about
                          identifying it precisely ( frequency) before asserting that it is identical.


                          > The consultant I referred to earlier, who was employed by the local
                          > council, used a C
                          > weighted meter to measure the hum. Hence the reading of 10 to 12.5
                          > Hz at 38dBs was
                          > most likely accurate. An A weighted meter doesn't measure sound as
                          > low as that.

                          Most meters have a switch that can be set to A or C weighting. An
                          unweighted (Z) reading would be more meaningful. That the meter was able to
                          measure at 10Hz would indicate that it was of the appropriate type and
                          quality. 38dBspl is quite quiet, and totally not the frequency you were
                          hearing. !). 10 Hz cannot be heard at all, thouigh harmonics might. A 10 Hz
                          could possibly be felt when exciting a large surface area. At 10Hz any
                          weighting is rather irrelevanrt as such frequencies are not heard anyway.


                          > Geoff, you said in another message:
                          >> Hum does sounds incredibly realistically ¡external¢, but isn¢t
                          >> necessarily so, otherwise I would be hearing it in BOTH ears now,
                          >> not just one.
                          >
                          > Hearing the hum in only one ear, more often the left, according to
                          > early messages in this
                          > forum, is one of the signs of the classical hum.

                          And that there is a sound that can be heard only in one ear tells you what
                          about the source of that sound ? I know what it tells me, and it isn't that
                          I am deaf in the other ear !

                          geoff
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