Amazon offers Prime members the Tacklife Sound Level Meter, model no. SLM01, for $29.99. Coupon code "XNHM9MPD" cuts it to $17.99. With free shipping, that's $62 off list and the lowest total price we could find. (Non-members can spend $49 or more to qualify for free shipping; otherwise, shipping costs $5.22.) It features an LCD display, measures 30 to 130 decibels, and uses a 9-volt battery.