Photoacoustic effect

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  • #574899
    Steve Harvey
    Participant

    I’ve just been reading an article discussing the possibility of meteors and aurora producing noise (human discernible audio).

    It sounds like a contentious issue, but I have found a paper on the subject. https://pubmed.ncbi.nlm.nih.gov/28145486/
    I wonder whether anyone has any further information they can shed on this subject. fact or fiction?

    #583877
    John Cook
    Participant

    The long distance between meteor trails / aurora and ground level means that there would be a long delay between the visual and acoustic, and so difficult to correlate. I have read that the strong electric fields associated with aurora can lead to static discharges on things like pine needles, leading to a crackiling noise. My only two experiences of the aurora were not accompanied by static noise, although I do remember hearing howling dogs at 2AM in Alaska while watching a good display nearly 30 years ago!

    #583878
    Robin Leadbeater
    Participant

    I used to work for a Swedish paper company and when discussing aurorae with a colleague who worked in forestry there he commented unprompted on hearing crackling during strong aurorae which I assumed was a local electrostatic effect.  

    #583880
    Paul Leyland
    Participant

    I have absolutely no idea whether this might be an explanation, but I believe that aurorae produce radio waves which can be picked up by radio receivers.

    There have been documented cases of unexpected diodes (akin to the good old cat’s whisker) producing audio outputs from AM radio transmissions. A few cases involved mercury amalgam dental fillings, for example.

    I wonder whether this may be relevant.

    #583884
    John Cook
    Participant

    Auroral curtains can certainly reflect radio waves, and are often used by radio amateurs to make contacts at VHF. There has been suggestions that meteors can produce VLF signals, but I have not received any reports of such reception. Having just had an amalgam dental filling, I will let you know if it starts working as a diode!

    #583885
    Callum Potter
    Keymaster

    There are certainly a lot of anecdotal stories from Orkney of people who have heard the aurora.

    Rebecca Marr of the Uni of the Highlands and Islands writes:

    Many accounts talk of the sound of the lights.  The Sami name guovsahasat has been translated by some as ‘the light you can hear’. A 1906 dissertation on the lights by Lane Cooper says:

    ‘It is a very general belief in certain countries – for instance in the Orkneys, in Finmark, and among the Indians of the territories around Hudson Bay – that the aurora is accompanied by a particular sound, somewhat resembling the rustling of silk. The Lapps, who also believe in the existence of this sound, compare it to the ‘cracking’ which may be heard in the joints of the reindeer when in movement.’

    Callum

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