Unfortunately, Pete Townshend Did Not Use The Information Services of Health Canada

From Health Canada:

Personal stereo systems offer a convenient way to listen to music in public without disturbing others. A typical system combines a portable cassette, compact disc player, or radio, with headphones or earphones. Scientific studies suggest that these devices may cause hearing loss if they are not used with a degree of caution....

Sounds with levels below 70 dBA pose no known risk of hearing loss, no matter how long they last. If you listen to music at 70 dBA, the sound level is about the same as what you experience while driving a four-door family car on the highway with the windows closed.

For sound levels higher than 70 dBA, the duration of daily exposure becomes an important risk factor. For example, sounds with levels of 85 dBA pose no known risk of hearing loss if you are exposed for no longer than 45 minutes per day. However, sound levels of 85 dBA or higher can pose a significant risk of permanent hearing loss, if you are exposed for eight hours per day....

Officials have reviewed scientific literature on personal stereo systems, and have conducted tests to assess their potential to cause hearing loss. These tests measured the sound levels generated at maximum volume settings using a variety of headphones/earphones, and portable compact disc (CD) players. The music selected for the tests included pop songs from the "top ten" charts, and heavy metal tracks.

The findings:

All combinations of headphones/earphones and CD players could generate potentially harmful sound levels

Pop music sound levels ranged from 86 to 102 dBA when researchers used the headphones that came packaged with the CD player. When researchers combined CD players with headphones purchased separately, the sound levels reached 114 dBA - test results also suggested that this was not necessarily the limit

If you played the pre-packaged systems at maximum volume, it would take from 12 minutes (at 102 dBA) to seven hours (at 86 dBA) to exceed the occupational noise limit noted above. Furthermore, you would exceed the limit in just one minute if you played heavy metal or pop music at full volume on the combination CD / headphone system that produced sound levels of 114 dBA. At this sound level, exposure for longer durations can pose a risk of immediate, serious and permanent hearing loss.

Another key finding was that sound levels from earbuds vary significantly from person to person, because the level depends on how well the "buds" fit into your ears. Tight-fitting earbuds tend to produce higher sound levels than other commercially available headphones....