Official 29 Set 3

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Reverberation

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What is the main purpose of the lecture?
  • A. To explain how musicians can perform successfully in theaters and concert halls with poor acoustics

  • B. To explain how the design of theaters and concert halls has changed over time

  • C. To discuss design factors that affect sound in a room

  • D. To discuss a method to measure the reverberation time of a room

显示答案 正确答案: C

我的笔记 编辑笔记

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    NARRATOR:Listen to part of a lecture in an architecture class.

    MALE PROFESSOR:Today I'd like to talk a bit about the relationship between the built world and sound- uh, the design of buildings like concert halls or theaters.So what's the most important aspect in the design of such a building?

    MALE STUDENT:Acoustics?

    MALE PROFESSOR:Yes. Now people have been concerned about how sound carries in auditoriums and theaters for at least 2,000 years, but it was not until the beginning of the twentieth century that architectural acoustics became a scientific field.That was when the physicist Wallace Sabine started to do extensive studies on reverberation.

    Sabine wanted to find out why the audience could not understand speakers at a lecture hall in Boston.He designed a series of studies on reverberation to figure it out.So what is reverberation? It's the persistence of sound in a room after the source has stopped making sound.You see, sound made in a room reflects off the walls, floor, and ceiling- that's the reverberant sound.The time it takes for the reverberant sound to die down is important for the acoustic quality of a room.Sabine recognized this, and he came up with an equation to measure a room's reverberation time.So, what happens if the reverberation time is very long?

    FEMALE STUDENT:Wouldn't it be difficult to hear new sounds if you can still hear the old sounds?

    MALE PROFESSOR:Exactly. A long reverberation time may cause musical notes to drown one another out.On the other hand, if the reverberation time is very short, meaning the reverberations are absorbed very quickly, the room is called "dead."Performers would feel they have to struggle to fill the room with sound.We don't want that. In a concert hall or theater, we prefer a "live" room, where the sound has fullness. So we need to control the reverberation time.After all, we don't want the listeners or the performers to have to struggle, right?So what are some important considerations when we design a theater or concert hall?

    MALE STUDENT:The size of the place?

    MALE PROFESSOR:Absolutely. The larger the room, the longer the reverberation time.So we'll have to take into account what the room will be mainly used for since music requires more reverberation than speech.A room intended for music needs to be designed differently from a room intended for drama.For music we need a very large room, a concert hall- actually, I-I should say for full orchestras-because for a single instrument, say, something like a piano recital, a room with a short reverberation time is better.So, for a solo piano, a smaller room works well. Yes?

    MALE STUDENT:I read that concert halls designed for symphony orchestras have too much echo for jazz music.

    MALE PROFESSOR:That doesn't surprise me- most small jazz groups would need rooms with a shorter reverberation time.But, besides the size of the room, another variable affecting reverberation is the shape of the room.Let's say you designed a rectangular, box-like space with bare walls and ceiling.This would allow the sound to act like a ball in a racquetball court, you know bouncing around and hitting some parts of the walls and ceiling but missing many others.If that happens in a concert hall, audience members may hear some sounds but not others.So what can be done to distribute the sound evenly in every direction?The answer is: avoid straight, parallel walls. Karen?

    FEMALE STUDENT:But I think I've seen photos of rectangular concert halls....

    MALE PROFESSOR:Right... Older concert halls from the 1800s are generally rectangular, but they all have a lot of decorations on the walls inside, lots of ornamental plasterwork like statues, which distribute sound very efficiently, reflecting it in all different directions.

    And that brings me to another variable we need to consider- the acoustic characteristics of the building materials as well as the wall and floor coverings.In fact, most objects you see in a concert hall or theater serve double duty.The plush chairs absorb sound and soften reverberation.And the beautiful crystal chandeliers? They are very good at diffusing sound.You see, everything must be planned down to the last detail in order to predict the acoustic performance of a room.That being said... there's something that can't be controlled by the architect.The audience has an effect on acoustics too- the heads of people are good diffusers of sound- and architects try to account for this effect in their design, but they can't guarantee a full auditorium!

  • 旁白:听一段建筑课程。

    教授:今天我想讲一点建筑和声音的关系,像是音乐厅或剧院的建筑设计。设计这些建筑时最重要的是什么?

    学生:音响效果?

    教授:是的,现在人们已经开始关注声音在礼堂和剧院里传播至少2000年了,但直到20世纪初,建筑声学才成为一个科学领域。当时,物理学家华莱士·萨比恩(Wallace Sabine)开始对混响进行广泛研究。

    赛宾想要找出在波士顿的一个讲堂里,为什么观众不能理解发言人的意思。他针对回声现象设计了一系列研究,来寻找真相。什么是回声现象?就是在房间中,声源停止发声后,声音仍然持续的现象。在房间里发出的声音,会在墙壁、地板和天花板反射回来,那就是回声。回声彻底消失所用的时间长短,对一个房间的音响效果至关重要。赛宾发现了这一点,他提出一个等式来测量房间的回声时间。那么,如果回声时间很长,会发生什么呢?

    学生:如果你还能听见之前的声音,要听新的声音不就很困难了吗?

    教授:对。长时间回声可能会导致音符一个压过一个。另一方面,假如回声时间很短……意味着回声吸收得很快,房间就被成为“死房间”。表演者会觉得他们要努力制造声音,填满房间。我们可不想这样。在音乐厅或剧院里,我们更喜欢“活房间”,即充满声音的房间。所以我们要控制好回声时间。毕竟,我们可不想听众或表演者拼尽全力,对吧?所以,在我们设计剧院或音乐厅时,什么是重要的考虑因素?

    学生:地方的大小?

    教授:对。房间越大,回声时间越长。所以我们要考虑房间的主要用途,因为音乐演奏比演讲来说,更需要回声。音乐演奏的房间设计必须不同于戏剧表演的房间设计。要演奏音乐,我们需要一个很大的房间,一个音乐厅,实际上,我应该这么说,能容纳整个管弦乐队的房间,因为只有一种乐器的话,比如一场钢琴独奏会,有较短回声时间的房间更好。所以,对钢琴独奏来说,小房间也不错。嗯?

    学生:我看到过,一些为交响乐团设计的音乐厅,若演奏爵士乐,会产生过多的回声。

    教授:我并不惊讶。大多数爵士乐团需要回声时间更短的房间。除了房间大小以外,另一影响回声的变量是房间形状。假如你设计了一个矩形的盒子状空间,里面都是裸墙和裸天花板。这会让声音像壁球场里的球一样,来回反弹,击到墙壁和天花的某些部分,另一些则击不到。如果这发生在音乐厅里,听众可能只能听到一些声音,别的听不到了。把声音向所有方向传播出去,要怎么办呢?答案是:不要用直立平行的墙壁。凯伦?

    学生:我觉得我见过长方体形状的音乐厅。

    教授:对。1800年左右的老式音乐厅基本上都是长方体形状的。但这些音乐厅的内墙都有很多装饰,很多水泥装饰物,比如雕像,这些装饰物能有效传播声音,朝不同方向反射。

    这就引到了另一个我们需要考虑的变量,建筑材料和墙壁及地板覆盖物的声学性质。事实上,大部分你在音乐厅或剧院看到的东西都有双重功能。绒面座椅能吸收声音,弱化回声。漂亮的水晶灯?它们用来扩散声音非常有用。为了预测房间的音响效果,所有的东西都要考虑到细节。话虽如此,有些东西是建筑师无法掌控的。观众本身也有声学影响,人的头部也能很好地漫射声音。建筑师尝试在设计中考虑这一因素,建筑师尝试在设计中考虑这一因素,但他们也不能保证礼堂是座无虚席的。

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    题型分析:主旨题

    原文定位

    Professor: Today I'd like to talk a bit about the relationship between the built world and sound. Uh, the design of buildings like concert halls or theaters.

    选项分析

    文章开门见山直接对aspect design 展开了讨论,然后分别讲解了acoustic 中的size, shape。最后描述了这个方法的局限性

    C选项即为对话核心的原文定位,是对全文主旨最准确的概括

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