{"id":1400,"date":"2003-09-22T09:22:02","date_gmt":"2003-09-21T22:22:02","guid":{"rendered":"http:\/\/hifi-writer.com\/wpblog\/?p=1400"},"modified":"2010-03-15T20:50:09","modified_gmt":"2010-03-15T09:50:09","slug":"infrasonic-squirms","status":"publish","type":"post","link":"http:\/\/hifi-writer.com\/wpblog\/?p=1400","title":{"rendered":"Infrasonic squirms"},"content":{"rendered":"

Some experimental types have been working out the effect of infrasonic sound on people’s emotional states<\/a>. The recipe: take a seven metre long pipe, stick a ‘long throw’ bass driver (woofer<\/a>) therein a third of the way down, then drive it with a 17 hertz<\/a> signal. Insert into live performances from time to time, then have the audience complete a questionnaire. Compare their feelings about the music when the infrasonic sound was on with their feelings when it was off. Apparently it had some effect.<\/p>\n

I am interested in their infrasonic<\/a> production apparatus. Not very much information is provided. Presumably the pipe is tuned to resonate at 17 hertz, and I imagine it would be designed to reduce harmonics<\/a> to the minimum possible. The problem with producing pure bass<\/a> is the harmonic distortion that is almost always generated. Let us say that the second harmonic is at, say, five per cent of the fundamental frequency<\/a> (measure some subwoofers and you’ll find that this isn’t an unusual number!) That equates to 26 decibels<\/a> quieter. But the sensitivity of the human ear drops off very sharply in the extreme bass regions. The Fletcher Munson curves<\/a> (which attempt to equate the sensitivity of the human ear across the frequency spectrum) suggest a fall-off in sensitivity of as much as twelve decibels per octave<\/a> in the bass (ie. between 40 and 80 hertz) and this drop-off likely becomes steeper the further into bass one descends. So high levels of distortion can result in audibility of an ‘infrasonic’ tone.<\/p>\n

Thanks to my brother Mark for the heads-up. Go visit his Website Images of Canberra<\/a> to see a stack of wonderful photos of Canberra and environs.<\/p>\n","protected":false},"excerpt":{"rendered":"

Some experimental types have been working out the effect of infrasonic sound on people’s emotional states. The recipe: take a seven metre long pipe, stick a ‘long throw’ bass driver (woofer) therein a third of the way down, then drive … Continue reading →<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":[],"categories":[6],"tags":[],"_links":{"self":[{"href":"http:\/\/hifi-writer.com\/wpblog\/index.php?rest_route=\/wp\/v2\/posts\/1400"}],"collection":[{"href":"http:\/\/hifi-writer.com\/wpblog\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"http:\/\/hifi-writer.com\/wpblog\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"http:\/\/hifi-writer.com\/wpblog\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"http:\/\/hifi-writer.com\/wpblog\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=1400"}],"version-history":[{"count":1,"href":"http:\/\/hifi-writer.com\/wpblog\/index.php?rest_route=\/wp\/v2\/posts\/1400\/revisions"}],"predecessor-version":[{"id":1401,"href":"http:\/\/hifi-writer.com\/wpblog\/index.php?rest_route=\/wp\/v2\/posts\/1400\/revisions\/1401"}],"wp:attachment":[{"href":"http:\/\/hifi-writer.com\/wpblog\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=1400"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/hifi-writer.com\/wpblog\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=1400"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/hifi-writer.com\/wpblog\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=1400"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}