<?xml version="1.0" encoding="utf-8"?><mads xmlns="http://www.loc.gov/mads/" xmlns:mods="http://www.loc.gov/mods/v3" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.loc.gov/mads/
mads.xsd"><authority><topic authority="http://AATesaurus.cultura.gencat.cat/aat/getty_en">opeidoscopes</topic></authority><related type="broader"><topic>sound devices</topic></related><variant type="other"><topic>opeidoscope</topic></variant> <note xml:lang="en"><![CDATA[ Instruments that give visual representation of sounds, consisting of  tubes closed at one end by a taught membrane with a small mirror attached to its centre, which vibrates in response to sound entering the tube at the open end, causing a spot of light reflected by the mirror on to a screen to vibrate with varying amplitude and frequency. ]]></note></mads>