The influence of bubbles on sound has long attracted the attention of physicists. In his 1920 book1 Sir William Bragg described sound absorption caused by foam in a glass of beer tapped by a spoon. Frank S. Crawford described and analyzed the change in the pitch of sound in a similar experiment and named the phenomenon the "hot chocolate effect."2 In this paper we describe a simple and robust experiment that allows an easy audio and visual demonstration of the same effect (unfortunately without the chocolate) and offers several possibilities for student investigations. In addition to the demonstration of the above effect, the experiments described below provide an excellent opportunity for students to devise and test explanations with simple equipment.
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机译：气泡对声音的影响早已引起物理学家的关注。威廉·布拉格爵士（Sir William Bragg）在其1920年的著作中1描述了用勺子轻敲一杯啤酒中的泡沫引起的声音吸收。弗兰克·S·克劳福德（Frank S. Crawford）在类似的实验中描述并分析了音高的变化，并将这种现象命名为“热巧克力效应”。2在本文中，我们描述了一个简单而强大的实验，可以轻松地进行音频和视频演示。效果相同（不幸的是没有巧克力），并且为学生调查提供了几种可能性。除了上述效果的证明之外，以下所述的实验还为学生提供了一个极好的机会，使学生可以使用简单的设备来设计和测试解释。
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