{"id":29426,"date":"2014-07-08T19:22:34","date_gmt":"2014-07-08T23:22:34","guid":{"rendered":"https:\/\/www.windturbinesyndrome.com\/static\/static\/?p=29426"},"modified":"2014-07-09T07:36:45","modified_gmt":"2014-07-09T11:36:45","slug":"there-is-a-pressure-pulsation-emitted-into-the-community-once-every-second","status":"publish","type":"post","link":"https:\/\/www.windturbinesyndrome.com\/static\/2014\/there-is-a-pressure-pulsation-emitted-into-the-community-once-every-second\/","title":{"rendered":"\u201cThere is a pressure pulsation emitted into the community once every second\u201d (Wind Turbine Noise Expert)"},"content":{"rendered":"

.<\/span><\/p>\n

Editor\u2019s note<\/em>: \u00a0Rick James<\/a> is, without doubt, one of North America’s\u00a0premier experts on wind turbine noise. \u00a0Unlike the great majority of noise engineers who have sold their souls and ethics to the wind energy industry, Mr. James can\u2019t be \u201cbought.\u201d \u00a0Together\u00a0with Rob Rand<\/a> and Steve Ambrose<\/a>, Rick<\/a> has exposed the deceit\u00a0and mendacity of wind company acoustic consultants \u2014 as in\u00a0their\u00a0fraudulent use of A-weighted noise measurements, for instance.<\/p>\n

We all\u00a0owe these three gentlemen a huge debt of gratitude.<\/p>\n

\"thump2\"<\/p>\n

\n
\n
\n

.<\/span>
\n\u2014 Richard James<\/a>, Noise Engineer (7\/8\/14). \u00a0Click for<\/span> PDF<\/a>, with all graphs included.<\/span><\/p>\n

As the blade passes the tower, the low frequency noise and infrasound is generated at a frequency related to the hub\u2019s rotation and number of blades. These pressure pulsations appear as tones during analysis, but are not heard as tones by most people. Instead, they may feel the pressure changes as pulsations, internal organ vibrations, or as a pain (like ear aches or migraines).<\/p>\n

This frequency is called the Blade Pass Frequency, often abbreviated as BPF.<\/p>\n

For modern utility-scale wind turbines, this frequency is at 1Hz or lower. \u00a0A three-bladed wind turbine with a hub rotation of 20 revolutions per minute (rpm) has a BPF of 1Hz. This means there is a pressure pulsation emitted into the community once every second. \u00a0At 15 rpm the BPF is 0.75 Hz; and at 10 rpm, 0.5 Hz.<\/p>\n

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When wind turbine blades rotate past the tower, a short pressure pulse occurs, producing a burst of infrasound. \u00a0When analyzed, the result is a well-defined array of tonal harmonics below 10 Hz.<\/p>\n

For impulsive sound of this type, the harmonics\u00a0are all \u201cphase-correlated.\u201d This means the peaks\u00a0of each occur at the same time. Thus, the peaks add\u00a0together in a linear fashion, with their individual maximum sound pressures all coinciding.<\/p>\n

Thus, for an impulse having 4 equal amplitude harmonics (BPF, 2nd, 3rd and 4th) each of the\u00a0same amplitude, the peak level is +12 dB. \u00a0Ten\u00a0equal harmonics would produce a peak level\u00a0of +20 dB.<\/p>\n

\"Rick<\/p>\n

 <\/p>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>","protected":false},"excerpt":{"rendered":"

. Editor\u2019s note: \u00a0Rick James is, without doubt, one of North America’s\u00a0premier experts on wind turbine noise. \u00a0Unlike the great majority of noise engineers who have sold their souls and ethics to the wind energy industry, Mr. James can\u2019t be \u201cbought.\u201d \u00a0Together\u00a0with Rob Rand and Steve Ambrose, Rick has exposed the deceit\u00a0and mendacity of wind company acoustic consultants \u2014 as in\u00a0their\u00a0fraudulent use of A-weighted noise measurements, for instance. We all\u00a0owe these three gentlemen a huge debt of gratitude. . \u2014 Richard James, Noise Engineer (7\/8\/14). \u00a0Click for PDF, with all graphs included. As the blade passes the tower, the low frequency noise and infrasound is generated at a frequency related to the hub\u2019s rotation and number of blades. These pressure pulsations appear as tones during analysis, but are not heard as tones by most people. Instead, they may feel the pressure changes as pulsations, internal organ vibrations, or as a pain (like ear aches or migraines). This frequency is called the Blade Pass Frequency, often abbreviated as BPF. For modern utility-scale wind turbines, this frequency is at 1Hz or lower. \u00a0A three-bladed wind turbine with a hub rotation of 20 revolutions per minute (rpm) has a BPF of 1Hz. This means there is a pressure pulsation emitted into the community once every second. \u00a0At 15 rpm the BPF is 0.75 Hz; and at 10 rpm, 0.5 Hz. When wind turbine blades rotate past the tower, a short pressure pulse occurs, producing a burst of infrasound. \u00a0When analyzed, the result is a well-defined array of tonal harmonics below 10 Hz. For impulsive sound of this type, the harmonics\u00a0are all \u201cphase-correlated.\u201d This means the peaks\u00a0of each occur at the same time. Thus, the peaks add\u00a0together in a linear fashion, with their individual maximum sound pressures all coinciding. Thus, for an impulse havingRead More…<\/a><\/p>\n","protected":false},"author":3,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":[],"categories":[157,163,16],"tags":[],"_links":{"self":[{"href":"https:\/\/www.windturbinesyndrome.com\/static\/wp-json\/wp\/v2\/posts\/29426"}],"collection":[{"href":"https:\/\/www.windturbinesyndrome.com\/static\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.windturbinesyndrome.com\/static\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.windturbinesyndrome.com\/static\/wp-json\/wp\/v2\/users\/3"}],"replies":[{"embeddable":true,"href":"https:\/\/www.windturbinesyndrome.com\/static\/wp-json\/wp\/v2\/comments?post=29426"}],"version-history":[{"count":0,"href":"https:\/\/www.windturbinesyndrome.com\/static\/wp-json\/wp\/v2\/posts\/29426\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.windturbinesyndrome.com\/static\/wp-json\/wp\/v2\/media?parent=29426"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.windturbinesyndrome.com\/static\/wp-json\/wp\/v2\/categories?post=29426"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.windturbinesyndrome.com\/static\/wp-json\/wp\/v2\/tags?post=29426"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}