壓縮波(compression waves or compressional waves)讯泣,也叫縱波(primary wave)或P波,水聲中一般其聲速符號為嫁艇。
剪切波(transverse wave)朗伶,也叫橫波(shear wave,secondary wave)或S波步咪,水聲中一般其聲速符號為论皆。
水中聲速一般記為或,w指water。海底聲速若記為点晴,則表示海底只考慮了壓縮波沒有考慮剪切波感凤,此時的含義等同于,b指bottom(根據(jù)上下文粒督,有時也指basement)陪竿。
水中密度和海底密度分別記為或。
海底衰減一般記為屠橄,此時指壓縮波衰減(海底只考慮了壓縮波沒有考慮剪切波)族跛,如果區(qū)分壓縮波衰減和剪切波衰減,應(yīng)記為或
當(dāng)考慮分層海底時锐墙,一般會用數(shù)字區(qū)分不同層海底的參數(shù):礁哄、、贮匕、姐仅、、刻盐、掏膏、、敦锌、馒疹。如果只考慮了壓縮波沒有考慮剪切波,也可直接記為乙墙、颖变、、听想、腥刹、。如果知道海底類型汉买,如具體類型mud衔峰、sand或者分類類型基底層(basement layer)、沉積層(sediment layer)蛙粘,也可將其作為下標(biāo)垫卤,如、出牧、穴肘、,不特別注明壓縮波和剪切波的舔痕,均認(rèn)為不考慮剪切波评抚。
Jensen的《計算海洋聲學(xué)》第38頁1.6節(jié)第一段:
When sound interacts with the seafloor, the structure of the ocean bottom becomes important. Ocean bottom sediments are often modeled as fluids which means that they support only one type of sound wave–a compressional wave. This is often a good approximation since the rigidity (and hence the shear speed) of the sediment is usually considerably less than that of a solid, such as rock. In the latter case, which applies to the ocean basement or the case where there is no sediment overlying the basement, the medium must be modeled as elastic, which means it supports both compressional and shear waves. In reality, the media are viscoelastic, meaning that they are also lossy.
翻譯:當(dāng)聲音與海底相互作用時豹缀,海底的結(jié)構(gòu)就變得很重要。海底沉積物通常被建模為流體慨代,這意味著它們只支持一種類型的聲波——壓縮波耿眉。這通常是一個很好的近似值,因?yàn)槌练e物的剛度(因此剪切速度)通常遠(yuǎn)小于固體(如巖石)的剛度鱼响。在后一種情況下,適用于海洋基底或基底上沒有沉積物的情況组底,介質(zhì)必須建模為彈性介質(zhì)丈积,這意味著它同時支持壓縮波和剪切波。事實(shí)上债鸡,介質(zhì)是粘彈性的江滨,這意味著它們也是有損耗的。