2m) test ducts are described in the informative Annexes H and I, respectively. The maximum mean flow velocity at the microphone head for which the method is suitable depends on the type of microphone shield used, and is as follows: — foam ball 15 m/s; — nose cone 20 m/s; — sampling tube 40 m/s. Above these values the suppression of turbulent pressure fluctuations by the microphone shield (see 3.9) may be insufficient. It is expected that sound power tests will be conducted in conjunction with airflow performance tests in accordance with ISO 5801. The ducting arrangement will therefore normally incorporate a "star" type flow straightener on the outlet side of the fan which will minimize swirl (see 7.3). Where it is permissible to delete the straightener as, for example, with large fans to installation category C according to ISO 5801:1997, the method is limited to a swirl angle of 15° (An example of a method for determining the angle of swirl is given in Annex J.) NOTE 2 The installation categories defined in ISO 5801 imply that the fan is either ducted on the outlet side only (category B), on the inlet side only (category C) or on both sides (category D). 2 Types of sound source The method described in this International Standard is applicable to a sound source in which a fan is connected to ducts on at least one side. It is also applicable to other fan/attenuator combinations or equipment incorporating fans which can be considered as "black boxes". Examples of fans and other equipment covered by this International Standard are — ducted centrifugal fans, — ducted axial flow fans, — ducted mixed-flow fans, — ducted air-handling units, — ducted dust-collection units, — ducted air-conditioning units, and — ducted furnaces. This International Standard is also applicable to other aerodynamic sources such as boxes, dampers and throttle devices provided that a quiet air flow delivered by an auxiliary fan is available, and the signal-to-noise ratio of sound pressures to turbulent pressure fluctuations in the test duct is at least 6 dB (see 7.2.1). An alternative method to determine the sound power level of the flow-generated noise of such aerodynamic sound sources, which does not require the measurement of sound pressure in a flow environment, is described in ISO 7235. The method was originally devised for the determination of the flow noise level of ducted silencers. The sound power is determined in a reverberation room connected to the test duct via a transition element. In the case of ducted fans with closely coupled attenuators, the signal-to-noise ratio of sound pressures to turbulent pressures may be insufficient when using the in-duct method. Therefore the method described in ISO 7235 is recommended for such fan/attenuator combinations. This International Standard is not applicable to non-ducted fans or equipment." >

BS EN ISO 5136:2003
声学.风机和其他鼓风装置吹到管道中的声功率的测定.管道法

Acoustics - Determination of sound power radiated into a duct by fans and other air-moving devices - In-duct method

2010-04

预览 BS EN ISO 5136:2003前三页
标准号
BS EN ISO 5136:2003
发布
2003年
发布单位
英国标准学会
替代标准
BS EN ISO 5136:2009
BS EN ISO 5136:2010
当前最新
BS EN ISO 5136:2010
 
 
适用范围
概述 本国际标准规定了一种测试管道风扇和其他空气输送装置的方法，以确定辐射到设备入口和/或出口侧消声端接管道中的声功率。 注 1：为简洁起见，文中凡出现“风扇”一词，均指“风扇或其他空气流动装置”。 该方法适用于发出稳定、宽带、窄带和离散频率声音的风扇，空气温度在- 50 ℃至+ 70 ℃之间。 测试管道直径范围为 0.15 m 至 2 m。 小型（d < 0.15 m）和大型（d > 2m）测试管道的测试方法分别在资料性附录 H 和 I 中描述。 该方法适用的麦克风头处的最大平均流速取决于所使用的麦克风护罩的类型，如下： 　——泡沫球 15 m/s； 　——鼻锥 20 m/s； 　——采样管 40 m/s。 高于这些值时，麦克风屏蔽（见 3.9）对湍流压力波动的抑制可能不够。 预计声功率测试将根据 ISO 5801 与气流性能测试一起进行。 因此，管道布置通常会在风扇出口侧包含一个“星”型气流矫直器，以最大限度地减少涡流（见 7.3） ）。 如果允许删除矫直器，例如根据 ISO 5801:1997 将大型风扇安装在 C 类安装中，则该方法仅限于 15° 的旋流角（确定旋流角的方法的示例）注 2：ISO 5801 中定义的安装类别意味着风机要么仅在出口侧（B 类）、仅在入口侧（C 类）或两侧（D 类）安装管道。 2 声源类型 本国际标准描述的方法适用于风扇至少一侧与管道连接的声源。 它也适用于其他风扇/衰减器组合或包含可被视为“黑匣子”的风扇的设备。 本国际标准涵盖的风机和其他设备的示例有： 　——管道离心风机; 　——管道轴流风机; 　——管道混流风机; 　——管道空气处理机组; 　——管道除尘机组; 　——管道空调机组、和——管道炉。 本标准也适用于其他空气动力源，如箱体、阻尼器和节流装置，前提是有辅助风扇提供安静的气流，并且测试中声压与湍流压力波动的信噪比管道噪声至少为 6 dB（见 7.2.1）。 ISO 7235 中描述了一种确定此类空气动力学声源的流动噪声的声功率级的替代方法，该方法不需要测量流动环境中的声压。 该方法最初设计用于确定管道消音器的流动噪声水平。 声功率是在通过过渡元件连接到测试管道的混响室中确定的。 对于具有紧密耦合衰减器的涵道风扇，使用管道内方法时，声压与湍流压力的信噪比可能不足。 因此，对于此类风扇/衰减器组合，建议采用 ISO 7235 中描述的方法。 本国际标准不适用于非管道式风扇或设备。

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