Speaking tube
（重定向自Voicepipe）
A speaking tube or voicepipe is a device based on two cones connected by an air pipe through which speech can be transmitted over an extended distance. While its most common use was in intra-ship communications, the principle was also used in affluent homes and offices of the 19th century, as well as expensive automobiles, military aircraft, and even locomotives. For most purposes, the device was outmoded by the telephone and its widespread adoption. This device was also known as a "megaphone", but that use has since become superseded.