[{"data":1,"prerenderedAt":774},["ShallowReactive",2],{"site-footer-common":3,"glossary:attenuation-acoustic":45,"glossary-related:attenuation-acoustic":153},{"id":4,"extension":5,"footer":6,"meta":40,"navbar":41,"stem":43,"__hash__":44},"common\u002Fcommon.yml","yml",{"tagline":7,"links":8,"sections":9},"Acoustic cleaning intelligence for industrial fouling, soot, ash, dust and build-up.",[],[10,19,31],{"title":11,"links":12},"Product",[13,16],{"label":14,"to":15},"How it works","\u002F#product",{"label":17,"to":18},"Cost assessment","\u002F#hero",{"title":20,"links":21},"Company",[22,25,28],{"label":23,"to":24},"What we build","\u002F#about",{"label":26,"to":27},"Careers","\u002F#careers",{"label":29,"to":30},"Contact","\u002F#contact",{"title":32,"links":33},"Resources",[34,37],{"label":35,"to":36},"Blog","\u002Fresources\u002Fblog",{"label":38,"to":39},"Glossary","\u002Fglossary",{},{"links":42},[],"common","YocmZRy1AYfBbpgGVms-zhdiABlF8VTxHx6h4rDmZBA",{"id":46,"title":47,"aliases":48,"body":51,"category":134,"description":135,"extension":136,"meta":137,"navigation":138,"path":139,"relatedTerms":140,"seo":144,"sources":147,"stem":151,"term":47,"__hash__":152},"glossary\u002Fglossary\u002Fattenuation-acoustic.md","Attenuation (acoustic)",[49,50],"acoustic attenuation","sound attenuation",{"type":52,"value":53,"toc":127},"minimark",[54,78,83,86,90,98,102],[55,56,57,61,62,67,68,72,73,77],"p",{},[58,59,60],"strong",{},"Attenuation"," is the loss of acoustic energy as a sound wave propagates through a medium. It combines geometric spreading (the ",[63,64,66],"a",{"href":65},"\u002Fglossary\u002Finverse-square-law","inverse-square law",") with absorption losses to viscosity, heat conduction and molecular relaxation. Attenuation rises sharply with ",[63,69,71],{"href":70},"\u002Fglossary\u002Ffrequency","frequency",", which is the physical reason ",[63,74,76],{"href":75},"\u002Fglossary\u002Flow-frequency-acoustic-cleaner","low-frequency acoustic cleaners"," reach further into large industrial vessels than their high-frequency counterparts.",[79,80,82],"h2",{"id":81},"implications-for-cleaning-reach","Implications for cleaning reach",[55,84,85],{},"A 60 Hz wave loses very little energy per metre of air travel; a 400 Hz wave loses substantially more. In hot flue gas the absolute losses change but the frequency dependence remains the same. The result is that a 60 Hz horn can clean fly-ash deposits 8–10 metres from the bell, while a 400 Hz horn is generally effective only within 3–4 metres at the same nameplate SPL.",[79,87,89],{"id":88},"implications-for-noise-control","Implications for noise control",[55,91,92,93,97],{},"The same physics that lets a low-frequency horn reach deep into a vessel also lets it travel further outside the vessel. Operator-station noise control is therefore harder for low-frequency installations, and ",[63,94,96],{"href":95},"\u002Fglossary\u002Fsound-attenuation-enclosure-sonic-horn","sound-attenuation enclosures"," are sometimes added at the bell.",[79,99,101],{"id":100},"related-terms","Related terms",[103,104,105,112,117,122],"ul",{},[106,107,108],"li",{},[63,109,111],{"href":110},"\u002Fglossary\u002Fwavelength","Wavelength",[106,113,114],{},[63,115,116],{"href":70},"Frequency",[106,118,119],{},[63,120,121],{"href":65},"Inverse-square law",[106,123,124],{},[63,125,126],{"href":95},"Sound-attenuation enclosure (sonic horn)",{"title":128,"searchDepth":129,"depth":129,"links":130},"",2,[131,132,133],{"id":81,"depth":129,"text":82},{"id":88,"depth":129,"text":89},{"id":100,"depth":129,"text":101},"acoustics-physics","Attenuation is the loss of acoustic energy as a sound wave propagates through a medium. It combines geometric spreading (the inverse-square law) with absorption losses to viscosity, heat conduction and molecular relaxation. Attenuation rises sharply with frequency, which is the physical reason low-frequency acoustic cleaners reach further into large industrial vessels than their high-frequency counterparts.","md",{},true,"\u002Fglossary\u002Fattenuation-acoustic",[141,71,142,143],"wavelength","inverse-square-law","sound-attenuation-enclosure-sonic-horn",{"title":145,"description":146},"Acoustic attenuation — why low-frequency sound travels further","Attenuation is the loss of acoustic energy as a sound wave propagates. Higher frequencies attenuate faster, which is why low-frequency sonic horns reach further in industrial vessels.",[148],{"title":149,"url":150},"Wikipedia — Acoustic attenuation","https:\u002F\u002Fen.wikipedia.org\u002Fwiki\u002FAcoustic_attenuation","glossary\u002Fattenuation-acoustic","WuKkiYEJRYbK7QdnPPy-tGtriMZpacuaLkpTV2w-RwM",[154,317,498,649],{"id":155,"title":111,"aliases":156,"body":159,"category":134,"description":301,"extension":136,"meta":302,"navigation":138,"path":110,"relatedTerms":303,"seo":308,"sources":311,"stem":315,"term":111,"__hash__":316},"glossary\u002Fglossary\u002Fwavelength.md",[157,158],"acoustic wavelength","sound wavelength",{"type":52,"value":160,"toc":296},[161,169,173,248,251,255,266,268],[55,162,163,165,166,168],{},[58,164,111],{}," is the spatial distance over which one full cycle of a wave repeats. It is calculated as λ = c \u002F f, where c is the speed of sound in the medium (~343 m\u002Fs in air at 20 °C) and f is the ",[63,167,71],{"href":70}," in hertz. For industrial acoustic cleaning the wavelength is the single most informative dimension because it predicts how the horn's sound field will fill the vessel.",[79,170,172],{"id":171},"wavelengths-for-industrial-sonic-horns","Wavelengths for industrial sonic horns",[174,175,176,188],"table",{},[177,178,179],"thead",{},[180,181,182,185],"tr",{},[183,184,116],"th",{},[183,186,187],{},"Wavelength in air at 20 °C",[189,190,191,200,208,216,224,232,240],"tbody",{},[180,192,193,197],{},[194,195,196],"td",{},"12 Hz",[194,198,199],{},"~28 m",[180,201,202,205],{},[194,203,204],{},"30 Hz",[194,206,207],{},"~11 m",[180,209,210,213],{},[194,211,212],{},"60 Hz",[194,214,215],{},"~5.7 m",[180,217,218,221],{},[194,219,220],{},"75 Hz",[194,222,223],{},"~4.6 m",[180,225,226,229],{},[194,227,228],{},"125 Hz",[194,230,231],{},"~2.7 m",[180,233,234,237],{},[194,235,236],{},"230 Hz",[194,238,239],{},"~1.5 m",[180,241,242,245],{},[194,243,244],{},"400 Hz",[194,246,247],{},"~0.85 m",[55,249,250],{},"Wavelengths in hot flue gas are longer than in cool air because the speed of sound rises with temperature — at 200 °C the speed of sound is about 436 m\u002Fs, stretching a 75 Hz wave to roughly 5.8 m.",[79,252,254],{"id":253},"why-long-wavelengths-penetrate-further","Why long wavelengths penetrate further",[55,256,257,258,260,261,265],{},"Acoustic energy diffracts efficiently around obstructions smaller than its wavelength. A 5-metre 60 Hz wave bends around tube rows, electrode spacings and baffles that would scatter or absorb a 1-metre 350 Hz wave. This is the underlying physics of why ",[63,259,76],{"href":75}," clean large open vessels better than ",[63,262,264],{"href":263},"\u002Fglossary\u002Fhigh-frequency-acoustic-cleaner","high-frequency"," units.",[79,267,101],{"id":100},[103,269,270,274,280,286,291],{},[106,271,272],{},[63,273,116],{"href":70},[106,275,276],{},[63,277,279],{"href":278},"\u002Fglossary\u002Fsound-pressure-level","Sound pressure level",[106,281,282],{},[63,283,285],{"href":284},"\u002Fglossary\u002Fstanding-wave","Standing wave",[106,287,288],{},[63,289,290],{"href":75},"Low-frequency acoustic cleaner",[106,292,293],{},[63,294,295],{"href":263},"High-frequency acoustic cleaner",{"title":128,"searchDepth":129,"depth":129,"links":297},[298,299,300],{"id":171,"depth":129,"text":172},{"id":253,"depth":129,"text":254},{"id":100,"depth":129,"text":101},"Wavelength is the spatial distance over which one full cycle of a wave repeats. It is calculated as λ = c \u002F f, where c is the speed of sound in the medium (~343 m\u002Fs in air at 20 °C) and f is the frequency in hertz. For industrial acoustic cleaning the wavelength is the single most informative dimension because it predicts how the horn's sound field will fill the vessel.",{},[71,304,305,306,307],"sound-pressure-level","standing-wave","low-frequency-acoustic-cleaner","high-frequency-acoustic-cleaner",{"title":309,"description":310},"Wavelength — how long is a sonic horn's wave inside a vessel?","Wavelength is the distance a sound wave travels in one cycle. At 60 Hz in air a wave is 5.7 m long; at 400 Hz it is 0.85 m. Wavelength governs how far a sonic horn's cleaning reach extends.",[312],{"title":313,"url":314},"Wikipedia — Wavelength","https:\u002F\u002Fen.wikipedia.org\u002Fwiki\u002FWavelength","glossary\u002Fwavelength","yrWaX9232a1ZSNJwMET2GxJuJPt98k9__zwmIHdRPuk",{"id":318,"title":319,"aliases":320,"body":324,"category":134,"description":484,"extension":136,"meta":485,"navigation":138,"path":70,"relatedTerms":486,"seo":489,"sources":492,"stem":496,"term":116,"__hash__":497},"glossary\u002Fglossary\u002Ffrequency.md","Frequency (Hz)",[321,322,323],"Hz","acoustic frequency","sonic horn frequency",{"type":52,"value":325,"toc":479},[326,338,342,431,435,447,449],[55,327,328,330,331,334,335,337],{},[58,329,116],{}," is the number of acoustic cycles per second, measured in hertz (Hz). For industrial acoustic cleaning it is the single most important selection parameter after ",[63,332,333],{"href":278},"SPL",": frequency determines ",[63,336,141],{"href":110},", which in turn governs how the sound wave penetrates the vessel.",[79,339,341],{"id":340},"industrial-cleaning-bands","Industrial cleaning bands",[174,343,344,360],{},[177,345,346],{},[180,347,348,351,354,357],{},[183,349,350],{},"Band",[183,352,353],{},"Range",[183,355,356],{},"Wavelength in air",[183,358,359],{},"Typical use",[189,361,362,385,410],{},[180,363,364,367,370,373],{},[194,365,366],{},"Infrasonic",[194,368,369],{},"12–30 Hz",[194,371,372],{},"11–28 m",[194,374,375,379,380,384],{},[63,376,378],{"href":377},"\u002Fglossary\u002Frecovery-boiler","Recovery boilers",", ",[63,381,383],{"href":382},"\u002Fglossary\u002Fwaste-to-energy","WtE"," flue paths",[180,386,387,390,393,396],{},[194,388,389],{},"Low frequency",[194,391,392],{},"60–250 Hz",[194,394,395],{},"1.4–5.7 m",[194,397,398,379,402,379,406],{},[63,399,401],{"href":400},"\u002Fglossary\u002Felectrostatic-precipitator","ESPs",[63,403,405],{"href":404},"\u002Fglossary\u002Fpreheater-cyclone","preheater cyclones",[63,407,409],{"href":408},"\u002Fglossary\u002Fsilo","silos",[180,411,412,415,418,421],{},[194,413,414],{},"High frequency",[194,416,417],{},"250–450 Hz",[194,419,420],{},"0.75–1.4 m",[194,422,423,379,427],{},[63,424,426],{"href":425},"\u002Fglossary\u002Ffabric-filter","Fabric filters",[63,428,430],{"href":429},"\u002Fglossary\u002Fselective-catalytic-reduction","SCR catalysts",[79,432,434],{"id":433},"trade-off","Trade-off",[55,436,437,438,442,443,446],{},"Long wavelengths diffract around obstructions and penetrate further; short wavelengths concentrate more energy in a smaller volume. The frequency choice is therefore a trade between ",[439,440,441],"em",{},"reach"," and ",[439,444,445],{},"energy density",". Many real installations combine both bands: low-frequency horns clean the bulk volume; high-frequency horns clean dense bag rows or catalyst faces.",[79,448,101],{"id":100},[103,450,451,455,459,465,469,473],{},[106,452,453],{},[63,454,111],{"href":110},[106,456,457],{},[63,458,279],{"href":278},[106,460,461],{},[63,462,464],{"href":463},"\u002Fglossary\u002Ffundamental-frequency","Fundamental frequency",[106,466,467],{},[63,468,290],{"href":75},[106,470,471],{},[63,472,295],{"href":263},[106,474,475],{},[63,476,478],{"href":477},"\u002Fglossary\u002Finfrasonic-cleaner","Infrasonic cleaner",{"title":128,"searchDepth":129,"depth":129,"links":480},[481,482,483],{"id":340,"depth":129,"text":341},{"id":433,"depth":129,"text":434},{"id":100,"depth":129,"text":101},"Frequency is the number of acoustic cycles per second, measured in hertz (Hz). For industrial acoustic cleaning it is the single most important selection parameter after SPL: frequency determines wavelength, which in turn governs how the sound wave penetrates the vessel.",{},[141,304,487,306,307,488],"fundamental-frequency","infrasonic-cleaner",{"title":490,"description":491},"Frequency (Hz) — selection bands for industrial sonic horns","Frequency is the number of acoustic cycles per second, measured in hertz. Industrial acoustic cleaners operate at 12–30 Hz (infrasonic), 60–250 Hz (low) or 250–450 Hz (high).",[493],{"title":494,"url":495},"Wikipedia — Frequency","https:\u002F\u002Fen.wikipedia.org\u002Fwiki\u002FFrequency","glossary\u002Ffrequency","7P2gkJzmA_x2ddonur2FhvOEPYFBCmPrnuK_ZNv8mqc",{"id":499,"title":121,"aliases":500,"body":503,"category":134,"description":635,"extension":136,"meta":636,"navigation":138,"path":65,"relatedTerms":637,"seo":640,"sources":643,"stem":647,"term":121,"__hash__":648},"glossary\u002Fglossary\u002Finverse-square-law.md",[501,502],"1\u002Fr² law (acoustic)","geometric spreading",{"type":52,"value":504,"toc":629},[505,518,522,525,579,583,595,599,612,614],[55,506,507,508,510,511,379,515,517],{},"The ",[58,509,66],{}," states that the intensity of a point-source sound wave falls as 1\u002Fr² with distance. Expressed in ",[63,512,514],{"href":513},"\u002Fglossary\u002Fdecibel","decibels",[63,516,333],{"href":278}," decreases by approximately 6 dB for every doubling of distance from the source in a free field.",[79,519,521],{"id":520},"worked-example-for-a-sonic-horn","Worked example for a sonic horn",[55,523,524],{},"A horn rated at 150 dB SPL at 1 m on the bell axis will produce, in free-field conditions:",[174,526,527,537],{},[177,528,529],{},[180,530,531,534],{},[183,532,533],{},"Distance",[183,535,536],{},"Approximate SPL",[189,538,539,547,555,563,571],{},[180,540,541,544],{},[194,542,543],{},"1 m",[194,545,546],{},"150 dB",[180,548,549,552],{},[194,550,551],{},"2 m",[194,553,554],{},"144 dB",[180,556,557,560],{},[194,558,559],{},"4 m",[194,561,562],{},"138 dB",[180,564,565,568],{},[194,566,567],{},"8 m",[194,569,570],{},"132 dB",[180,572,573,576],{},[194,574,575],{},"16 m",[194,577,578],{},"126 dB",[79,580,582],{"id":581},"where-the-rule-breaks-down","Where the rule breaks down",[55,584,585,586,590,591,594],{},"Three real conditions modify the textbook result. Inside a vessel, reflections from walls and tube banks reinforce the sound field and slow the fall-off; geometry no longer behaves as a free field. In the ",[63,587,589],{"href":588},"\u002Fglossary\u002Fnear-field-far-field","near field"," of the bell, the simple 1\u002Fr² rule does not apply. And at long distances and high frequencies, ",[63,592,593],{"href":139},"attenuation"," absorbs additional energy beyond geometric spreading.",[79,596,598],{"id":597},"why-it-matters-for-noise-exposure","Why it matters for noise exposure",[55,600,601,602,606,607,611],{},"Worker exposure assessments work backwards from the inverse-square law: knowing the nameplate SPL and the operator-station distance, the predicted exposure can be compared with ",[63,603,605],{"href":604},"\u002Fglossary\u002Fosha-29-cfr-1910-95","OSHA 29 CFR 1910.95"," or ",[63,608,610],{"href":609},"\u002Fglossary\u002Feu-directive-2003-10-ec","EU Directive 2003\u002F10\u002FEC"," action levels.",[79,613,101],{"id":100},[103,615,616,620,624],{},[106,617,618],{},[63,619,279],{"href":278},[106,621,622],{},[63,623,47],{"href":139},[106,625,626],{},[63,627,628],{"href":588},"Near field \u002F far field",{"title":128,"searchDepth":129,"depth":129,"links":630},[631,632,633,634],{"id":520,"depth":129,"text":521},{"id":581,"depth":129,"text":582},{"id":597,"depth":129,"text":598},{"id":100,"depth":129,"text":101},"The inverse-square law states that the intensity of a point-source sound wave falls as 1\u002Fr² with distance. Expressed in decibels, SPL decreases by approximately 6 dB for every doubling of distance from the source in a free field.",{},[304,638,639],"attenuation-acoustic","near-field-far-field",{"title":641,"description":642},"Inverse-square law — sound pressure halves every doubling of distance","In free-field conditions sound intensity falls as 1\u002Fr². Sound pressure level drops by approximately 6 dB for each doubling of distance from the source.",[644],{"title":645,"url":646},"Wikipedia — Inverse-square law","https:\u002F\u002Fen.wikipedia.org\u002Fwiki\u002FInverse-square_law","glossary\u002Finverse-square-law","EYJdDFIbE5CXCp0ONbKYLs6jeZE8zRgWkX6myn6g82k",{"id":650,"title":126,"aliases":651,"body":655,"category":758,"description":759,"extension":136,"meta":760,"navigation":138,"path":95,"relatedTerms":761,"seo":765,"sources":768,"stem":772,"term":126,"__hash__":773},"glossary\u002Fglossary\u002Fsound-attenuation-enclosure-sonic-horn.md",[652,653,654],"sound enclosure","acoustic enclosure","noise-attenuation enclosure",{"type":52,"value":656,"toc":753},[657,679,683,697,701,732,734],[55,658,659,660,663,664,668,669,671,672,442,675,678],{},"A ",[58,661,662],{},"sound-attenuation enclosure"," surrounds a ",[63,665,667],{"href":666},"\u002Fglossary\u002Fsonic-horn","sonic horn"," installation to reduce the external ",[63,670,333],{"href":278}," experienced at the operator station, walkways and plant boundary. Typical SPL reduction is 10–25 dB depending on enclosure design — significant enough to bring exposures within ",[63,673,674],{"href":604},"OSHA",[63,676,677],{"href":609},"EU 2003\u002F10\u002FEC"," action limits at most realistic operator distances.",[79,680,682],{"id":681},"when-enclosures-are-specified","When enclosures are specified",[103,684,685,688,691,694],{},[106,686,687],{},"Sonic horns mounted close to operator-access walkways or maintenance positions",[106,689,690],{},"Multi-horn arrays where cumulative SPL exceeds the limit even at modest distance",[106,692,693],{},"Plant boundaries close to residential or commercial property",[106,695,696],{},"Indoor installations where reflection raises ambient SPL",[79,698,700],{"id":699},"trade-offs","Trade-offs",[103,702,703,709,720,726],{},[106,704,705,708],{},[58,706,707],{},"Cost"," — enclosures typically add 10–20% to the installed cost of the horn system",[106,710,711,714,715,719],{},[58,712,713],{},"Maintenance access"," — must be designed to allow routine ",[63,716,718],{"href":717},"\u002Fglossary\u002Fdiaphragm-replacement-sonic-horn","diaphragm replacement"," and inspection",[106,721,722,725],{},[58,723,724],{},"Thermal management"," — for hot-side installations, enclosure ventilation must prevent overheating of accessories",[106,727,728,731],{},[58,729,730],{},"Slight SPL reduction inside the vessel"," — usually marginal, but worth checking in marginal-coverage cases",[79,733,101],{"id":100},[103,735,736,741,745,749],{},[106,737,738],{},[63,739,740],{"href":666},"Sonic horn",[106,742,743],{},[63,744,279],{"href":278},[106,746,747],{},[63,748,605],{"href":604},[106,750,751],{},[63,752,610],{"href":609},{"title":128,"searchDepth":129,"depth":129,"links":754},[755,756,757],{"id":681,"depth":129,"text":682},{"id":699,"depth":129,"text":700},{"id":100,"depth":129,"text":101},"controls-ancillaries","A sound-attenuation enclosure surrounds a sonic horn installation to reduce the external SPL experienced at the operator station, walkways and plant boundary. Typical SPL reduction is 10–25 dB depending on enclosure design — significant enough to bring exposures within OSHA and EU 2003\u002F10\u002FEC action limits at most realistic operator distances.",{},[762,304,763,764],"sonic-horn","osha-29-cfr-1910-95","eu-directive-2003-10-ec",{"title":766,"description":767},"Sound-attenuation enclosure — reduces sonic-horn noise at the work area","A sound-attenuation enclosure surrounds the sonic horn to reduce SPL at the operator station. Typical 10–25 dB reduction; required where horn proximity exceeds OSHA \u002F EU action levels.",[769],{"title":770,"url":771},"Wikipedia — Noise control","https:\u002F\u002Fen.wikipedia.org\u002Fwiki\u002FNoise_control","glossary\u002Fsound-attenuation-enclosure-sonic-horn","FR-H0qOqUvf8TGgdJbftenNX1Kg25JjWSxU9992_BLY",1782613716034]