Instruct: Classify the given Amazon review as either positive or negative.
Query: not useful for filtering out human voices

I bought this product because I sometimes want to concentrate on my work in the lab but there are other people chatting loud. However I found this earmuff not an idea product for this purpose. I guess it works to filter out most of the high frequency noises (background noises from cars, machines and other things) but didn't do well in the range of human talking--it only decreases the volumn. Effectively this is making the human voice even more obvious since now the background sound is lowered. It may still be good if you want to filter out machine noise in working conditions, which I didn't test.