The horn obviously is a brass instrument and what makes the sound is a vibrating column of air.

显而易见的,圆号是个铜管乐器,它通过震动空气柱来发出声音

耶鲁公开课 - 聆听音乐课程节选

For those of you don't know what that is it's simply an instrument that counts radioactive particles in the air, and MIT now that you're at MIT, you'll all have a chance to see one first hand if you're ever in any of the labs, especially in the chemistry or bio labs.

不知道它是什么,它就是一个简单的,计算在空气中放射粒子数目的仪器,你们现在来了，如果你们在实验室里工作的话,尤其是化学和生物实验室，你们有很多机会亲手用到它。

麻省理工公开课 - 化学原理课程节选