Look and listen, and that concert poster just might be singing. Engineers have designed antennas（天线）that can turn everyday objects, from posters to clothing, into radio stations. Anyone walking or driving by can tune in and hear what’s on. The devices use radio waves, but they don’t generate their own. They hijack（劫持）the same waves that carry music and news to your smartphone.

Vikram Iyer co-led the project with Anran Wang, a graduate student in computer science and engineering. The two got the idea for their invention by paving attention to what was already around them. “It's the ideal way to minimize the power consumption for any kind of communication,” notes Iyer. Their research had focused on new types of wireless communications that won’t require much energy. They wanted something that would work outdoors in a city. Then they realized the air is already filled with wireless communications in the form of radio stations.

Radio waves carry energy at the speed of light from tall transmission towers to radios in cars, phones and homes. These waves of the antennas take in existing radio waves and change them slightly. Those changes add new sound information. The changed waves are then sent back out into the world where people can listen in. So the device only needs enough power to change the waves, not to generate them.

The scientists tested their device with a poster. It advertised a Seattle concert by Simply Three. People standing almost 4 meters away from the poster could use FM receivers on smartphones to listen to all songs of the band's music. Those in cars as far as 18 meters away could use car radios to pick up some parts of the songs.

The technology could even extend to clothes. Iyer, Wang and their team turned the shirt into an antenna. It let the shirt talk to the wearer’s smartphone. If a sensor in the shirt tracked a person’s heart rate during exercise, for instance, the antenna could transmit those data to the wearer’s phone.

Every day, millions of people surf the Internet, and there are countless websites for them to visit. Here are four popular websites for online users.

https://www. cracked. com

If you’re old enough, you might remember Cracked, the monthly magazine that was founded in 1958. Although the magazine is no longer printed, the website hutps://uwww. crached. com is still alive. The content(内容)of Cracked is humorous and tries to tell readers something new and unexpected.

https://www. buzzfeed. com

Are you looking for links to big news on the Internet? Look no further than hutps://www. buzafeed. com. Each day the website offers the latest stories and pictures that are crazily spread. BuzzFeed covers different topics and its articles are written by staff members, site users, and partner sites like The Huffington Post and The Daily Beast.

https://www. reddit. com

Reddit calls itself“the front page of the Internet”, and that is exactly what it is. Just as many people used to read the newspaper while eating breakfast, one to two million Internet users read Reddit every morning to get their daily news. The content of this website comes entirely from the public, with users uploading(上传) videos, links, stories, pictures, etc.

https://imgur. com

Do you know many of the funny pictures, GIFs and emojis(表情符号) that hit your Facebook come from Imgur? It’s a free website where users upload 1. 5 million pictures each day. Imgur users are especially fond of pictures of cute animals and beautiful natural wonders. And it is free to read and use. You can download any photo you like.

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