Qualitative behaviour of L1 and L2 standard deviation in insulations measurements according to standard UNE EN ISO 140-4

Knowledge of the uncertainty of measurement of testing results is important when results have to be compared with limits and specifications. In the measurement of sound insulation following standards UNE EN ISO 140-4 the uncertainty of the final magnitude is mainly associated to the average sound pressure levels L1 and L2 measured. A parameter that allows us to quantify the spatial variation of the sound pressure level is the standard deviation of the pressure levels measured at different points of the room. In this work, for a wide number of measurements following standards UNE EN ISO 140-4 we analyzed qualitatively the behaviour of the standard deviation for L1 and L2. The study of sound fields in enclosed spaces is very difficult. There are a wide variety of rooms with different sound fields depending on factors as volume, geometry and materials. In general, we observe that the L1 and L2 standard deviations contain peaks and dips independent on characteristics of the rooms at single frequencies that could correspond to critical frequencies of walls, floors and windows or even to temporal alterations of the sound field. Also, in most measurements according to UNE EN ISO 140-4 a large similitude between L1 and L2 standard deviation is found. We believe that such result points to a coupled system between source and receiving rooms, mainly at low frequencies the shape of the L1 and L2 standard deviations is comparable to the velocity level standard deviation on a wall

A comparison of the results obtained by the complement fixation test for the diagnosis of syphilis performed according to the new technique of Kolmer and the technique of the California state hygienic laboratory,

Thesis (M.A.)--Univ. of California. Dec. 1922.

British mezzotinto portraits : being a descriptive catalogue of these engravings from the introduction of the art to the early part of the present century : arranged according to the engravers, the inscriptions given at full length, and the variations of state precisely set forth : accompanied by biographical notes, and appendix of a selection of the prices produced at public sales by some of the specimens, down to the present time /

Includes indexes.

Book of the dead: the chapters of Coming forth by day; the Egyptian text according to the Theban recension in hieroglyphic,

v. 1.--The Egyptian text in hieroglyphic.--v. 2. An English translation with introduction, notes, etc.--v. 3. A vocabulary in hieroglyphic.

The domestic ritual according to the school of Bhāradvāja,

Sanskrit title at head of title-page.

The traditional games of England, Scotland, and Ireland, with tunes, singing-rhymes, and methods of playing according to the variants extant and recorded in different parts of the Kingdom;

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The ancient liturgy of the Church of England, according to the uses of Sarum, York, Hereford, and Bangor, and the Roman liturgy arranged in parallel columns with preface and notes,

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Mode of access: Internet.

The Holy Bible, according to the authorized version (A.D. 1611), with an explanatory and critical commentary and a revision of the translation, by bishops and other clergy of the Anglican church.

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Syn Theo : The two holy sacraments of Baptism and of the Lord's Supper, according to Scripture, grammar and the Faith /

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Includes bibliographical references.

A flora of North America: containing abridged descriptions of all the known indigenous and naturalized plants growing north of Mexico; arranged according to the natural system.

Mode of access: Internet.

A syllabic dictionary of the Chinese language : arranged according to the Wu-fang Yuen Yin, with the pronunciation of the characters as heard in Peking, Canton, Amoy, and Shanghai /

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