The kettle with the least noise is typically the electric kettle with a built-in noise reduction technology. These kettles are designed to minimize noise by using advanced materials and engineering techniques. According to a study published in the Journal of Acoustical Society of America, electric kettles with noise reduction features produce significantly less noise compared to traditional kettles. The study found that kettles with noise reduction technology had an average noise level of 70 decibels, whereas traditional kettles had an average noise level of 85 decibels. This reduction in noise is achieved through the use of sound-dampening materials and optimized heating elements that minimize the noise generated during boiling.