MIT World系列：音乐的各种声音

关于本次演讲
你曾经想过为何车子以某一时速在高速公路特定路段行驶时，会发出怪声吗？或是为什么长笛的音调高于伸缩号？Lewin教授利用橡胶水管、有孔的木盒、金属盘以及其它自制的装置来示范物体如何发声。所有问题最后会回归到物体如何振动：把空气推挤至四面八方。
Have you ever wondered about the annoying hum your car makes at a certain speed on a particular stretch of highway? Or why a flute’s notes are higher than a trombone’s? Walter Lewin uses rubber hose, wooden boxes with holes, metal plates and an assortment of other home-made instruments to demonstrate how objects produce sound. It all boils down to how something vibrates — pushing air out in all directions.

Lewin教授说明「声音的样貌」，用一条仅固定一端的绳子，然后用不同速度甩动使其产生不同波状。这波状即绳子的共振频率，或称谐音。这跟演奏小提琴有异曲同工之妙，因为弦的振动会产生一阵阵谐音，发出我们听到的音调──振动越快，音调就越高。Lewin教授还从观众席邀请了几位小孩上台演奏乐器，示范声音的振幅及频率。之后，他播放一段影片说明毁灭性的共振，片中桥梁因扭曲过度而崩塌。接着，回到实验室，当场示范如何让酒杯因越来越大声且越来越高的音调而被震碎。这场演讲融合物理学与表演艺术，Lewin教授将让你惊喜连连。
Lewin illustrates the shape of sounds, taking a rope tethered at one end, shaking it up and down at different speeds and producing specific wave shapes. These shapes are the rope’s resonant frequencies, or harmonics. It’s the same for a bowed violin, where the oscillations of the strings generate a set of harmonics, producing the notes we hear — the faster the oscillations, the higher the tones. Lewin invites children from the audience to produce sounds with their musical instruments, and shows the amplitude and frequency of the tones. Later he demonstrates destructive resonances: video of a bridge that twists so violently that it collapses, and then, live in the laboratory, the shattering of a wine glass with progressively louder and higher tones. In this event where physics meets performance art, Lewin provides surprises throughout.

关于讲者

Walter H. G. Lewin在麻省理工学院以牛顿力学课程和电磁学课程闻名，授课影片可以在网络上的开放式课程及下方连结观看。
Walter H. G. Lewin is well-known at MIT for his lectures on both Newtonian mechanics and electricity and magnetism. Videos of his lectures can be viewed on the web via the Open CourseWare and Pivot links below.
Lewin在1965年于荷兰的代尔夫特理工大学取得核物理学博士学位，1966年后一直以来在麻省理工学院担任物理教师。在麻省理工学院任教时，他研究天体物理学，包括卫星与高空气球X射线观测、光学与X射线爆全球协调观测、及X射线源国际观测合作。另外，这些年来Lewin教授也与不同的艺术家合作各项苍穹艺术项目。1998年到2000年间，他参与麻省理工学院高等教育服务中心的物理互动教学影片辅导计划，让大学新鲜人更了解物理。
Lewin received his Ph.D. in Nuclear Physics in 1965 at the Technical University of Delft, The Netherlands, and has been a member of the MIT Physics faculty since 1966. During his MIT career, Lewin’s investigations in astrophysics have included satellite and high-altitude balloon X-ray observations, world-wide coordinated observations of optical and X-ray bursts, and international collaborations observing X-ray sources. In addition, Lewin has collaborated over the years with various artists on sky art events. From 1998 to 2000, Lewin worked with MIT’s Center for Advanced Educational Services on creating the Physics Interactive Video Tutor project — video help sessions for freshman physics students.

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关于MIT World
MIT World是免费、开放式的串流媒体网站，记录麻省理工学院重大公开活动，有近期来自全校和世界各地的主讲者和贵宾，本专案隶属於麻省理工学院工学院的的专业教育课程。
MIT World挑选的影片内容首重大眾的兴趣，应属於学术或相关主题，但同时是多数观眾都能了解的，内容范围可涵盖最新的资讯，在科学、工程、建筑、人类学、艺术暨科学、科技暨管理等领域，还有关於技术、或者是阐述社会、艺术、人类学概况的特定研讨会和演讲报告。MIT World网站不含公共关係、行政、人力资源沟通，也不是一个新闻网站，不过可经由网站连结至其他相关首页、资源、麻省理工学院新闻室或其他学院、研究室、系所和办公室，那里会提供背景资料和更多讯息。

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