Walmart offers the Sony ZX Series Noise-Canceling Headphones in Black, model no. MDR-ZX110NC, for $20.88. Opt for free in-store pickup to avoid the $5.97 shipping charge. That's $27 under January mention (which included a $25 Dell gift card) and the lowest price we've seen. (It's a current low by $14.) They feature a frequency response of 12Hz to 22kHz, 10 dB/mW sensitivity, and 45 Ohm impedence.