Barrera-Figueroa Salvador
Danish Fundamental Metrology A/S, Matematiktorvet 307, 2800 Kongens Lyngby, Denmark.
J Acoust Soc Am. 2018 Oct;144(4):2575. doi: 10.1121/1.5063815.
Microphones are typically calibrated in a free field at frequencies up to 40 kHz using primary and secondary methods. This upper frequency is sufficiently high as to cover most sound measurement applications related with airborne noise assessment. However, other applications such as measurement of noise emitted by ultrasound cleaning machines, failure detection in aeronautic structures, and the investigation of the perception mechanisms of ultrasound may require that the sensitivity of the microphone is known at frequencies up to 150 kHz. In any of these applications, it is critical to establish a well-defined traceability chain to SI units to support any measurement result. In order to extend the frequency range of absolute free-field calibration, typical reciprocity measurement systems and measurement methods must undergo a series of changes and adaptations which may include using other types of microphones rather than laboratory standard microphones, changing the type of measurement signal, improving the methods for eliminating unwanted reflections from walls, cross-talk, distortion, etc. Herein, a strategy for the changes and adaptations to the existing measurement methodologies, and the determination of the microphone parameters is outlined, the results of its implementation are discussed, and calibrations results are presented and discussed.
麦克风通常在自由场中使用一级和二级方法在高达40kHz的频率下进行校准。这个上限频率足够高，足以涵盖与空气传播噪声评估相关的大多数声音测量应用。然而，其他应用，如超声清洗机发出的噪声测量、航空结构中的故障检测以及超声感知机制的研究，可能需要知道麦克风在高达150kHz频率下的灵敏度。在任何这些应用中，建立一个明确的到国际单位制（SI）单位的可追溯链以支持任何测量结果至关重要。为了扩展绝对自由场校准的频率范围，典型的互易测量系统和测量方法必须进行一系列的改变和调整，这可能包括使用其他类型的麦克风而非实验室标准麦克风、改变测量信号类型、改进消除来自墙壁的不需要的反射、串扰、失真等的方法。在此，概述了对现有测量方法进行改变和调整以及确定麦克风参数的策略，讨论了其实施结果，并给出并讨论了校准结果。
