This is what I use when I need to focus at work Audio-Technica ATH-ANC7B QuietPoint Active Noise-Cancelling Closed-Back Headphones https://www.amazon.com/dp/B002HWJT1A/ref=cm_sw_r_awd_s5ZJvbX3TMRAB
They filter out most noise well. Conversations can be tough to filter out since they aren't like white noise. They do significantly lower the volume of them though which is normally enough for me. I've heard that the bose headphones filter those out the best, but I haven't tried them. I'd still recommend these headphones for most situations where you want to filter out noise.