{"id":3952,"date":"2010-09-17T16:03:35","date_gmt":"2010-09-17T16:03:35","guid":{"rendered":"http:\/\/www.megalithia.com\/sound\/?p=6"},"modified":"2020-07-03T14:37:17","modified_gmt":"2020-07-03T14:37:17","slug":"resonant-bridge","status":"publish","type":"post","link":"https:\/\/www.richardmudhar.com\/blog\/2010\/09\/resonant-bridge\/","title":{"rendered":"Resonant Bridge"},"content":{"rendered":"

Resonant Bridge, contact mic<\/p>\n

\"the<\/p>\n

 <\/p>\n

Resonant Bridge, contact mic with no mass coupling to back of element<\/p>\n

Resonant Bridge, contact mic with mass coupling to back of element<\/p>\nhttps:\/\/www.richardmudhar.com\/sounds\/audio\/060817_bridge_piezo_mass_2.mp3<\/a><\/audio>\n

To a man with a contact mic mounted on a magnet, every sound source looks like a large lump of steel, same way as the guy with a hammer sees nothing but nails…<\/p>\n

My luck was in when I came across this concrete footbridge across a dual carriageway. So I set up, carefully placing myself over the central reservation so drivers don’t get paranoid I’m about to zap ’em with a speed camera or throw stones or drop magnets on them. You get some funny looks attaching magnets and a piece of wire to a bridge by the other people, and the regional Police HQ is only 1\/2 mile away. This unpreposessing bridge has a decent tone to it, presumably ringing to the vibration of the traffic passing by. Which was awesomely noisy – you don’t realise just how loud the tyre noise is on a road until you try and cycle a stretch like this and find your ears ringing afterwards. The contact mic worked its usual magic in getting rid of all this racket.<\/p>\n

Resonant Bridge, traffic noise, OKMII binaurals w battery box<\/p>\nhttps:\/\/www.richardmudhar.com\/sounds\/audio\/060817_traffic.mp3<\/a><\/audio>\n

The two recordings with the contact mic were made, one with the mic held to the bridge with a strong magnet, the other with the same mic held to the bridge in the same way, but with an approx 0.5kg weight acting as a reaction mass on the other side of the piezo, to see if this picked up low frequencies better. You can hear the difference – or not, for yourself!<\/p>\n

\"\"
the traffic seen from the footbridge<\/figcaption><\/figure>\n

Piezo contact mics<\/a> seem to cause a lot of pain for people losing low frequencies, but I do not feel I am short of low frequencies here, using a basic FET buffer<\/a>. The peaks of the bridge resonance are 120Hz, 240Hz, 380Hz, 760Hz. There is, however, energy at 22 and 43 Hz at -36dB on the resonant peak, at a similar level to the broad peak around 3kHz which is probably the percussive sounds amplified by the piezo self resonance. The piezo was a Maplin YU87U 27mm 1.8kHz item terminated in 3.9Mohms, but the circuit could be improved to work better with a HiMD recorder mic input of 5k.<\/p>\n","protected":false},"excerpt":{"rendered":"

Resonant Bridge, contact mic   Resonant Bridge, contact mic with no mass coupling to back of element Resonant Bridge, contact mic with mass coupling to back of element To a man with a contact mic mounted on a magnet, every sound source looks like a large lump of steel, same way as the guy with … Continue reading “Resonant Bridge”<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"jetpack_post_was_ever_published":false,"_jetpack_newsletter_access":"","_jetpack_dont_email_post_to_subs":false,"_jetpack_newsletter_tier_id":0,"_jetpack_memberships_contains_paywalled_content":false,"_jetpack_memberships_contains_paid_content":false,"footnotes":"","jetpack_publicize_message":"","jetpack_publicize_feature_enabled":true,"jetpack_social_post_already_shared":true,"jetpack_social_options":{"image_generator_settings":{"template":"highway","default_image_id":0,"font":"","enabled":false},"version":2}},"categories":[237],"tags":[107,59,63],"class_list":["post-3952","post","type-post","status-publish","format-standard","hentry","category-sounds","tag-contact-mic","tag-experimental","tag-urban"],"jetpack_publicize_connections":[],"jetpack_featured_media_url":"","jetpack_sharing_enabled":true,"jetpack_shortlink":"https:\/\/wp.me\/p5aOO7-11K","jetpack_likes_enabled":true,"_links":{"self":[{"href":"https:\/\/www.richardmudhar.com\/blog\/wp-json\/wp\/v2\/posts\/3952","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.richardmudhar.com\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.richardmudhar.com\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.richardmudhar.com\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.richardmudhar.com\/blog\/wp-json\/wp\/v2\/comments?post=3952"}],"version-history":[{"count":4,"href":"https:\/\/www.richardmudhar.com\/blog\/wp-json\/wp\/v2\/posts\/3952\/revisions"}],"predecessor-version":[{"id":4271,"href":"https:\/\/www.richardmudhar.com\/blog\/wp-json\/wp\/v2\/posts\/3952\/revisions\/4271"}],"wp:attachment":[{"href":"https:\/\/www.richardmudhar.com\/blog\/wp-json\/wp\/v2\/media?parent=3952"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.richardmudhar.com\/blog\/wp-json\/wp\/v2\/categories?post=3952"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.richardmudhar.com\/blog\/wp-json\/wp\/v2\/tags?post=3952"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}