http://www.chemical-records.co.uk/s...o?Track=ALPLUGS

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Yes. Love them!

They bring down the volume of the audio frequencies uniformly so it doesn't sound muffled. You can cut the end piece to size so they are barely noticeable. I comfortably wear my headphones over them every time I DJ. I highly recommend them for anyone who wants to still have their hearing in 20 years.

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Temporarily retired from the world of DJing.

how many dB do they lower?

There are three different attachments for different levels of sound reduction. Here's a chart for the attenuation values at different frequencies: http://earplugstore.stores.yahoo.net/alnasoearpl.html

(It's not exactly the same attenuation value at each frequency but it's not supposed to be.)

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Temporarily retired from the world of DJing.