If two sources of equal loudness are added, what is the resultant increase in sound pressure level?

When two sources of equal loudness are combined, the increase in sound pressure level is approximately 3 dB. This phenomenon is based on the logarithmic nature of sound measurement, where the decibel scale measures relative changes in sound intensity.

When two identical sound sources are active, each contributes to the total sound intensity. While it might seem intuitive to think that the sound level would simply double, it does not work that way due to the logarithmic scale of decibels. Instead, the doubling of power results in an increase of 3 dB. This is mathematically derived from the fact that an increase of 10 dB corresponds to a tenfold increase in intensity. Therefore, when combining two equal sources, the increase results in approximately a 3 dB increase in sound pressure level.

In practical terms, this means that if you have two speakers producing the same sound, the perceived loudness will be noticeably greater than the sound from a single speaker, represented as a 3 dB increase in level. This knowledge is important for audiology technicians to understand how sound combines in real-world scenarios and how to assess sound levels accurately.