A holding part is provided for connecting two pipes running parallel to each other, such as the two parallel measuring pipes of a Coriolis mass flowmeter, at a defined spacing. The polycarboxylic acid ester contains an acid moiety having at least two carboxylic groups, and at least two alcohol moieties independently selected from those corresponding to a cycloalkyl alcohol or an aryl alcohol. The first and second rooms are designed for temporary use and can be easily disassembled for transport from one location to another. Deuterium gas, hydrogen gas, mixture gas with deuterium, or mixture gas with hydrogen is enclosed in the discharge vessel 1 as discharge gas. The method of extracting an important frequency component of an audio signal includes converting an audio signal of a time domain into an audio signal of a frequency domain, selecting a frequency band having a harmonic feature from the converted audio signal of the frequency domain, and extracting an important frequency component from the selected frequency band having the harmonic feature.