【英语科技】给静音汽车加点噪音

For decades, car designers and regulators have been trying to make vehicles more quiet. Now, with the advent of near-silent electric and hybrid vehicles, the industry is shifting into reverse.

Experts at the Geneva-based United Nations Economic Commission for Europe--the body responsible for harmonizing global vehicle regulations--are working on a set of minimum noise standards designed to keep quiet vehicles from becoming a safety risk to pedestrians.

The push is especially critical for groups like the blind, who rely on being able to hear vehicles to avoid being hit.

But it could create friction with noise-abatement advocates, who have welcomed the development of quieter vehicles, thrilled by the possibility that bird song might one day replace engine noise as the soundtrack in some urban settings.

So far, Japan is the only country to have come up with voluntary noise guidelines for makers of electric and hybrid vehicles, but the government is leaving it up to individual manufacturers to decide on the type of sound a vehicle will make.

The result is a wide variety of sounds that some industry watchers are already calling noise pollution.

Car makers say noise-making equipment is really necessary only when quiet cars are traveling at speeds of 20 kilometers an hour or less. Any faster and car tires make enough noise on the road surface to be heard.

'The danger zone is when cars are starting up, reversing and maneuvering at relatively slow speeds,' says Vincent Roussarie, a psycho-acoustician at French car maker PSA Peugeot-Citroen SA, who is studying the interaction between sounds and humans and is working on creating sounds for future electric vehicles.

'We want to solve the safety issue without transforming the 30-kilometers-an-hour zone into urban cacophony,' one of the reasons why global regulations are needed, says Roussarie.

Peugeot-Citroen, which plans to start selling its near-silent electric city cars, the Peugeot iOn and Citroen C-Zero, later this year, has teamed up with fellow French auto maker Renault SA (RNO.FR) to find ways to make electric vehicles more audible.

Roussarie is looking for sounds that let pedestrians know a car is approaching and where it is located. That means ensuring the sounds convey information, such as direction and speed, and whether the vehicle is accelerating or slowing.

In addition, 'we should be looking a little bit more carefully at character. Sound levels don't tell you everything. You can have a sound that's quite pleasant at a particular level, but you might not associate it with an oncoming vehicle,' says Jennings of Warwick University.
The sounds should be more sophisticated than a steady buzzing or musical sound, the jarring beep-beep made by reversing trucks or the jangle of ice-cream-van bells. The noises will need to be loud and distinctive enough to alert pedestrians, but not so jarring as to jolt people awake when they are in bed, says Roussarie.

Sound regulations also may eventually apply to traditional internal combustion engines, which are getting smaller and quieter every year because of increasingly tough emissions standards, Roussarie says. Hubert of UNECE says electric bicycles and mopeds also may be affected.

One challenge researchers have identified is to produce a sound that guide dogs for the blind can identify as an approaching car.

'Technically, it's not a problem to insert high-frequency sounds that only dogs can hear. The problem is to avoid a car waking up all the dogs in a neighborhood as it passes through,' Roussarie says. The dog-audible frequency would be blended into the main sound, Roussarie explains.

Another challenge facing car makers is that conventional engines and their vibrations tend to cover up a car's other squeaks, rattles and thuds. 'When you don't have an engine's noise, you hear everything that engine noise hid,' Roussarie says.

Bloomberg News标致雪铁龙公司计划开始销售Citroen C-Zero，且正在研究如何让这些车的声音更加明显。
几十年来，汽车设计师与监管方一直在尽力降低汽车的噪音。而现在，随着近乎无声的电动与混合动力汽车的出现，该行业正在向相反方向转变。

设在日内瓦的联合国欧洲经济委员会(United Nations Economic Commission for Europe)的专家们正在制定一套保持汽车最低噪音的标准，旨在防止静音车辆给行人带来安全风险。联合国欧洲经济委员会是负责协调全球汽车管制条例的机构。

这一举措对于依靠听音来避开车辆的盲人等群体来说尤其重要。

但这可能遭到削减噪音倡议者的反对，这类倡议者欢迎开发噪音更小的车辆，并为有一天城市背景声中鸟鸣会取代汽车马达的噪音而雀跃不已。

迄今为止，日本是唯一一个出台电动及混合动力汽车制造商自愿噪音准则的国家，但日本政府将车辆具有何种噪音的决定权留给制造商自行确定。

结果是噪音多种多样，以致某些行业观察人士将这称为噪音污染。

汽车制造商说，只有当静音汽车以20公里或以下时速行驶时才真正需要噪音发生装置。时速比这快时，汽车轮胎在路面产生的噪音足够引起人们注意了。

法国汽车制造商标致雪铁龙(PSA Peugeot Citroen SA)的心理声学家Vincent Roussarie从事人类与声音相互作用的研究，目前正在进行为未来的电动车制造声音的工作，他说，危险区是当汽车启动、倒车及以较低速度行驶时。

他希望不必将时速30公里变成城市噪音区就能解决这一安全问题，这也是需要全球性管制条例的原因之一。

标致雪铁龙计划今年晚些时候开始销售其制造的近静音型城市电动汽车Peugeot iOn与Citroen C-Zero。该公司已与法国雷诺公司(Renault SA)合作以寻求使电动汽车声音更明显的方法。

Roussarie正在寻找某种声音，以让行人知道汽车正在驶近且可辨别出汽车所在的方位。这意味着要确保声音传递诸如方向与速度，以及汽车是否在加速或减速等信息。

此外，英国华威大学(Warwick University)的詹宁斯(Jennings)说，还要多加注意声音的特点。声音的强度不会告诉你全部信息。你可以听到某种强度的声音相当悦耳，但可能不会联想到一辆汽车正在驶来。

Roussarie说，相比持续的嗡嗡声或音乐声、卡车倒车发出的嘟嘟声或流动雪糕车的刺耳声，这种声音应更为复杂。这种噪音需足够响亮而独特以警示行人，但又不至于太过刺耳把仍在睡梦中的人们吵醒。

Roussarie说，声音方面的管制也会最终适用于传统的内燃机。随着排放标准越来越严格，内燃机排放量越来越小，噪音也越来越低。联合国欧洲经济委员会的休伯特(Hubert)说，电动自行车与机动自行车也会受影响。

研究人员认为，其中一个挑战是要产生一种声音，使导盲犬能辨别出一辆汽车正在驶近。

Roussarie说，从技术上说，插入仅有狗才能听到的高频音不是问题。但问题是要避免一辆汽车经过时唤醒整个街区的狗。Roussarie解释说，会将狗可辨别的音频与主要的声音混合。

汽车制造商面临的另一问题是，传统的发动机及振动通常会盖过汽车的其它吱吱、嘎嘎及砰砰等噪音。Roussarie说，如果马达没有了噪音，你就会听到这种噪音遮盖住的一切声响。