吸(xi)(xi)聲(sheng)(sheng)(sheng)(sheng)是聲(sheng)(sheng)(sheng)(sheng)波(bo)撞擊到材(cai)(cai)料表面后(hou)能(neng)(neng)量損失的(de)(de)現象(xiang)，吸(xi)(xi)聲(sheng)(sheng)(sheng)(sheng)可(ke)(ke)以降(jiang)低室(shi)內聲(sheng)(sheng)(sheng)(sheng)壓級(ji)。描述吸(xi)(xi)聲(sheng)(sheng)(sheng)(sheng)的(de)(de)指標(biao)是吸(xi)(xi)聲(sheng)(sheng)(sheng)(sheng)系數a,代表被材(cai)(cai)料吸(xi)(xi)收的(de)(de)聲(sheng)(sheng)(sheng)(sheng)能(neng)(neng)與入(ru)射(she)(she)聲(sheng)(sheng)(sheng)(sheng)能(neng)(neng)的(de)(de)比(bi)值。理論上(shang)，如果(guo)某(mou)(mou)種材(cai)(cai)料完(wan)全(quan)反(fan)射(she)(she)聲(sheng)(sheng)(sheng)(sheng)音，那(nei)么它的(de)(de)a=0;如果(guo)某(mou)(mou)種材(cai)(cai)料將入(ru)射(she)(she)聲(sheng)(sheng)(sheng)(sheng)能(neng)(neng)全(quan)部(bu)(bu)吸(xi)(xi)收，那(nei)么它的(de)(de)a=1.事實上(shang)，所有材(cai)(cai)料的(de)(de)a介于0和1之間，也就是不(bu)可(ke)(ke)能(neng)(neng)全(quan)部(bu)(bu)反(fan)射(she)(she)，也不(bu)可(ke)(ke)能(neng)(neng)全(quan)部(bu)(bu)吸(xi)(xi)收。

　　不(bu)同(tong)頻(pin)(pin)率上會有不(bu)同(tong)的(de)吸(xi)(xi)聲(sheng)(sheng)(sheng)系(xi)(xi)數(shu)(shu)。人(ren)們使用吸(xi)(xi)聲(sheng)(sheng)(sheng)系(xi)(xi)數(shu)(shu)頻(pin)(pin)率特性(xing)曲線描述材(cai)(cai)(cai)(cai)料(liao)(liao)(liao)在不(bu)同(tong)頻(pin)(pin)率上的(de)吸(xi)(xi)聲(sheng)(sheng)(sheng)性(xing)能。按照ISO標(biao)準和國家標(biao)準，吸(xi)(xi)聲(sheng)(sheng)(sheng)測(ce)試報告中吸(xi)(xi)聲(sheng)(sheng)(sheng)系(xi)(xi)數(shu)(shu)的(de)頻(pin)(pin)率范(fan)圍是100-5KHz.將 100-5KHz的(de)吸(xi)(xi)聲(sheng)(sheng)(sheng)系(xi)(xi)數(shu)(shu)取平(ping)(ping)均(jun)得到的(de)數(shu)(shu)值(zhi)是平(ping)(ping)均(jun)吸(xi)(xi)聲(sheng)(sheng)(sheng)系(xi)(xi)數(shu)(shu)，平(ping)(ping)均(jun)吸(xi)(xi)聲(sheng)(sheng)(sheng)系(xi)(xi)數(shu)(shu)反(fan)映了材(cai)(cai)(cai)(cai)料(liao)(liao)(liao)總體的(de)吸(xi)(xi)聲(sheng)(sheng)(sheng)性(xing)能。在工程中常使用降噪系(xi)(xi)數(shu)(shu)NRC粗略地評價在語言頻(pin)(pin)率范(fan)圍內(nei)的(de)吸(xi)(xi)聲(sheng)(sheng)(sheng)性(xing)能，這(zhe)一數(shu)(shu)值(zhi)是材(cai)(cai)(cai)(cai)料(liao)(liao)(liao)在250、500、1K、2K四個頻(pin)(pin)率的(de)吸(xi)(xi)聲(sheng)(sheng)(sheng)系(xi)(xi)數(shu)(shu)的(de)算術平(ping)(ping)均(jun)值(zhi)，四舍(she)五入取整到0.05.一般認(ren)為(wei)NRC小于0.2的(de)材(cai)(cai)(cai)(cai)料(liao)(liao)(liao)是反(fan)射材(cai)(cai)(cai)(cai)料(liao)(liao)(liao)，NRC大(da)于等0.2的(de)材(cai)(cai)(cai)(cai)料(liao)(liao)(liao)才被認(ren)為(wei)是吸(xi)(xi)聲(sheng)(sheng)(sheng)材(cai)(cai)(cai)(cai)料(liao)(liao)(liao)。當(dang)需要吸(xi)(xi)收大(da)量聲(sheng)(sheng)(sheng)能降低室內(nei)混響(xiang)及(ji)噪聲(sheng)(sheng)(sheng)時，常常需要使用高吸(xi)(xi)聲(sheng)(sheng)(sheng)系(xi)(xi)數(shu)(shu)的(de)材(cai)(cai)(cai)(cai)料(liao)(liao)(liao)。

　　測量(liang)(liang)材(cai)料吸(xi)聲(sheng)系(xi)(xi)(xi)數(shu)(shu)(shu)的(de)(de)(de)(de)方(fang)(fang)(fang)法(fa)(fa)有兩種(zhong)(zhong)(zhong)，一(yi)種(zhong)(zhong)(zhong)是(shi)混(hun)響(xiang)室(shi)法(fa)(fa)，一(yi)種(zhong)(zhong)(zhong)是(shi)駐波管法(fa)(fa)。混(hun)響(xiang)室(shi)法(fa)(fa)測量(liang)(liang)聲(sheng)音無規入(ru)(ru)射時的(de)(de)(de)(de)吸(xi)聲(sheng)系(xi)(xi)(xi)數(shu)(shu)(shu)，即聲(sheng)音由四面八方(fang)(fang)(fang)射入(ru)(ru)材(cai)料時能(neng)量(liang)(liang)損失的(de)(de)(de)(de)比例，而駐波管法(fa)(fa)測量(liang)(liang)聲(sheng)音正入(ru)(ru)射時的(de)(de)(de)(de)吸(xi)聲(sheng)系(xi)(xi)(xi)數(shu)(shu)(shu)，聲(sheng)音入(ru)(ru)射角度僅為90度。兩種(zhong)(zhong)(zhong)方(fang)(fang)(fang)法(fa)(fa)測量(liang)(liang)的(de)(de)(de)(de)吸(xi)聲(sheng)系(xi)(xi)(xi)數(shu)(shu)(shu)是(shi)不(bu)同的(de)(de)(de)(de)，工程(cheng)上(shang)最(zui)常使用的(de)(de)(de)(de)是(shi)混(hun)響(xiang)室(shi)法(fa)(fa)測量(liang)(liang)的(de)(de)(de)(de)吸(xi)聲(sheng)系(xi)(xi)(xi)數(shu)(shu)(shu)，因為建筑實(shi)際應用中聲(sheng)音入(ru)(ru)射都是(shi)無規的(de)(de)(de)(de)。在某些測量(liang)(liang)報告中會出現吸(xi)聲(sheng)系(xi)(xi)(xi)數(shu)(shu)(shu)大于(yu)1的(de)(de)(de)(de)情況，這是(shi)由于(yu)測量(liang)(liang)的(de)(de)(de)(de)實(shi)驗室(shi)條件(jian)等造成的(de)(de)(de)(de)，理論(lun)上(shang)任何材(cai)料吸(xi)收的(de)(de)(de)(de)聲(sheng)能(neng)不(bu)可(ke)能(neng)大于(yu)入(ru)(ru)射聲(sheng)能(neng)，吸(xi)聲(sheng)系(xi)(xi)(xi)數(shu)(shu)(shu)永遠小于(yu)1.任何大于(yu)1的(de)(de)(de)(de)測量(liang)(liang)吸(xi)聲(sheng)系(xi)(xi)(xi)數(shu)(shu)(shu)值在實(shi)際聲(sheng)學工程(cheng)計算中都不(bu)能(neng)按(an)大于(yu)1使用，最(zui)多按(an)1進行(xing)計算。

　　在房間中，聲(sheng)(sheng)音會很快充滿各個角(jiao)落，因(yin)此，將吸(xi)(xi)(xi)聲(sheng)(sheng)材料放置(zhi)在房間任何表(biao)面都(dou)有吸(xi)(xi)(xi)聲(sheng)(sheng)效(xiao)果。吸(xi)(xi)(xi)聲(sheng)(sheng)材料吸(xi)(xi)(xi)聲(sheng)(sheng)系數越(yue)大，吸(xi)(xi)(xi)聲(sheng)(sheng)面積越(yue)多，吸(xi)(xi)(xi)聲(sheng)(sheng)效(xiao)果越(yue)明顯。可以利用(yong)吸(xi)(xi)(xi)聲(sheng)(sheng)天花、吸(xi)(xi)(xi)音板、聚酯纖維吸(xi)(xi)(xi)音板、空間吸(xi)(xi)(xi)聲(sheng)(sheng)體(ti)等進行(xing)吸(xi)(xi)(xi)聲(sheng)(sheng)降噪。