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Category: (((—Acoustics Engineering—))))

  • General Features of a Ventilation System

    In many countries, HVAC systems have come into widespread use in residential and commercial buildings (small houses, apartments, shops, stores, warehouses, hotels, and large office buildings, etc.). The energy sources for the systems include gas, oil, and electricity. In residential housing the heating or cooling medium can be air, water, steam, or refrigerant requiring ducting,…

  • Interior Noise Level Design Criteria

    When specifying interior noise level objectives for different areas of a building, many factors have to be considered. In general, the ventilation system noise should be low enough so as not to interfere with speech or other communicative sounds. In determining the acceptability of the air‐conditioning system noise, it is necessary not only to aim…

  • Introduction

    There is widespread use of heating ventilation and air‐conditioning (HVAC) systems in a variety of small and large buildings. The main consideration facing the designer of such systems is to ensure that the plant provides the required amount of heated or cooled air throughout the building and does not create objectionable noise or vibration either in the…

  • 12.9.4 Control of Vibration of Buildings Caused by Strong Wind

    Structures such as buildings immersed in a moving fluid experience fluid loading forces. These forces are caused by several physical phenomena. The phenomena may be divided into three main categories: (i) steady incoming flow that impinges on the structure, (ii) unsteady incoming flow, and (iii) eddies (vortices) that form in the fluctuating wake flowing past…

  • Impact Sound Transmission

    Impact noise is other major sound transmission problem in buildings. Although transmission of airborne sound is probably the major problem, the secondary problem of sound transmission from impacts such as footsteps, doors slamming, hammering and other forms of construction, etc. has concerned acousticians for many years. Footsteps are the main source. There are two main…

  • Single‐Number Ratings for Partitions

    When comparing different wall constructions, it is often convenient to use a single‐number rating instead of the complicated transmission loss (or normalized NR) which varies with frequency. Early single‐number ratings were obtained by simply averaging the TL (or normalized NR) in the frequency range of interest. Although such a system may be useful in rating walls, it…

  • 12.7.2 Measurements of Transmission Loss in the Field

    It is difficult to obtain the idealized conditions of random incidence, diffuse sound fields, and absence of flanking transmission in laboratory situations. In real buildings (field conditions), such conditions are impossible to obtain in practice. However, as discussed before, it is sometimes necessary to determine the TL of a partition in the field where flanking transmission is present.…

  • Sound Transmission Measurement Techniques

    There are several reasons for making sound transmission measurements, including: (i) to make tests under standardized laboratory conditions which should give repeatable comparisons of the performance of different partition structures and materials, (ii) to conduct laboratory tests in development work on partitions to indicate changes in sound TL which are caused by small design changes, (iii) to decide…

  • Effects of Leaks and Flanking Transmission

    Leaks in a wall frequently occur in practice and are very serious. Unless great care is taken in construction, leaks will occur and the theoretical TL of a wall will not be achieved. This effect is particularly noticeable at high frequency where the TL of a wall would be expected to be high. In this region, a leak can…

  • Transmission Through Composite Walls

    Often partitions are composed of several different elements, such as a brick wall having windows and doors. The average transmission loss TLav of this composite structure can be calculated as follows: suppose τ1 is the transmission coefficient of element of area S1, etc. and that a diffuse reverberant sound field of intensity εc/4 (where ε is the energy density in the incident field…