Measuring sound’s impact on human hearing is more complex than gauging its physical intensity. While decibels serve as a widely recognized unit for sound measurement, they primarily quantify sound pressure levels. This measurement does not always align with how humans perceive loudness. A specialized unit known as the sone was developed to bridge this gap, focusing on the subjective experience of sound.
Understanding the Sone
A sone is a psychoacoustic unit of perceived loudness, directly reflecting how loud a sound “feels” to a listener. It takes into account the complexities of human hearing rather than just the physical energy of sound waves. One sone is defined as the loudness of a 1000 Hz (Hertz) tone at 40 phons, which corresponds to a sound pressure level of 40 dB SPL (decibels Sound Pressure Level). This standardized reference point allows for consistent measurement of perceived loudness across different sounds. The sone scale operates linearly, meaning a sound perceived as twice as loud as one sone will have a value of two sones, and a four-sone sound is perceived to be twice as loud as a two-sone sound, making sone ratings intuitive for understanding relative loudness as experienced by the human ear.
Sones Compared to Decibels
Sones and decibels differ in what they measure and how their scales operate. Decibels (dB) measure sound pressure level, a physical property of sound waves, using a logarithmic scale. This means a small dB increase represents a large increase in sound intensity; for example, a 10 dB increase signifies a tenfold increase. This does not equate to a tenfold increase in perceived loudness.
Sones, in contrast, measure perceived loudness on a linear scale, aligning more closely with human auditory experience. For instance, a 60 dB sound might be perceived as only roughly twice as loud as a 50 dB sound, illustrating decibels’ non-linear nature in relation to human hearing. Sones account for how the human ear processes different frequencies and intensities, making them a more intuitive measure of perceived loudness. This distinction is important because human ears do not perceive all frequencies at the same loudness, even if their decibel levels are identical.
Real-World Applications of Sones
Sones find practical application in rating the loudness of household appliances, providing consumers with a clearer understanding of expected noise levels. This is useful for appliances where quiet operation is desirable. Bathroom fans, for instance, often have sone ratings from less than 0.3 sones for very quiet models to 6.0 sones for louder ones. A 1.0 sone fan is comparable to a running refrigerator, while 0.5 sones might be similar to rustling leaves.
Range hoods also commonly feature sone ratings, helping users choose models for their kitchen. Quiet range hoods typically fall within 1 to 4 sones, suitable for a peaceful kitchen. Moderate noise levels are usually between 4 and 6 sones, while louder models can exceed 6 sones.
Dishwashers and refrigerators are more commonly rated in decibels. Modern dishwashers range from 38 to 62 dBA, with quiet models often below 45 dBA. Refrigerators typically operate between 32 and 47 dB, with those below 40 dB considered quiet. Understanding these ratings helps consumers make informed purchasing decisions, especially when prioritizing a quiet home.