WEBVTT 1 00:00:00.877 --> 00:00:03.620 What is noise? 2 00:00:04.197 --> 00:00:06.950 Is this noise? 3 00:00:06.950 --> 00:00:08.877 Or this? 4 00:00:09.890 --> 00:00:11.986 And what about this? 5 00:00:13.520 --> 00:00:18.260 Pleasant and espected sounds usually aren't perceived as noise. 6 00:00:19.300 --> 00:00:21.970 Noise is sound that bothers us. 7 00:00:21.980 --> 00:00:26.113 What qualifies as noise can vary – the same sound one person enjoys 8 00:00:26.113 --> 00:00:28.423 might be noise to someone else. 9 00:00:28.867 --> 00:00:31.680 Noise is also related to loudness. 10 00:00:31.680 --> 00:00:35.530 When a sound exceeds a certain volume, it’s perceived as too loud. 11 00:00:35.530 --> 00:00:38.912 Sound levels are measured in decibels, or dB. 12 00:00:38.920 --> 00:00:44.670 For example, a ticking clock is around 30 decibels, traffic about 70 decibels, 13 00:00:44.670 --> 00:00:48.137 and a jet engine at takeoff reaches a staggering 140 decibels. 14 00:00:49.937 --> 00:00:52.340 Pitch also plays a role. 15 00:00:52.350 --> 00:00:56.110 High-pitched or shrill sounds are generally perceived as more 16 00:00:56.110 --> 00:00:58.766 unpleasant than lower-pitched ones. 17 00:00:59.187 --> 00:01:01.390 Duration is another factor. 18 00:01:01.400 --> 00:01:06.110 The longer we're exposed to a sound, the more strain it places on our hearing. 19 00:01:06.560 --> 00:01:11.080 Noise is also sound that we're unable to avoid. 20 00:01:11.520 --> 00:01:16.440 Sound waves travel in all directions, so it's not all that easy to escape. 21 00:01:19.667 --> 00:01:23.720 Sound that's too loud can cause permanent hearing damage 22 00:01:23.720 --> 00:01:26.230 faster than you might expect. 23 00:01:26.230 --> 00:01:31.569 And constant exposure to noise also increases the risk of cardiovascular disease. 24 00:01:32.717 --> 00:01:36.360 Noise protection can help minimize the negative effects. 25 00:01:36.440 --> 00:01:39.610 This protection can be either direct or indirect. 26 00:01:39.720 --> 00:01:43.680 Direct noise protection focuses on reducing noise at its source. 27 00:01:44.120 --> 00:01:48.280 For example, researchers are working on sound-dampening road surfaces 28 00:01:48.400 --> 00:01:50.986 and noise-reducing tires. 29 00:01:52.240 --> 00:01:56.220 Speed limits can also do a lot to reduce traffic noise. 30 00:01:57.873 --> 00:02:02.613 Indirect noise protection works by interrupting the spread of sound waves. 31 00:02:02.840 --> 00:02:06.000 Sound barriers along busy roads are one example. 32 00:02:06.280 --> 00:02:10.443 And tunnels can also indirectly reduce traffic noise.