Question about decibels

[phant0m0o0o]

So i have this question I am trying to answer where it asks which of the following features of a sound wave would necessarily result in an increase in its decibel level.

The choices are speed, wavelength, amplitude and frequency.

As I recalled Intensity is proportional to amplitude squared and frequency squared.

So wouldnt both increase intensity and therefore increase dB = 10 log i/i0 ?

Or am I just reading the question wrong and its asking about inherent property of the sound wave not changing its aspects? Thanks for your time.

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[portlandpixie]

I would say that an increase in decibel level would cause the amplitude of the wave to change/increase. The decibel system is a way of measuring the intensity/loudness of a sound such that if you have an increase in decibel level, you are increasing the amount of energy being transferred per unit area. And, as what you said, intensity is proportional to the amplitude squared and frequency squared. However, I think it is important to realize that intensity can either be a result of amplitude OR frequency and that a change in amp or frequency, while they both increase intensity, result in two different forms of intensity. If amplitude is increased, you increase the intensity by making the sound louder/delivering more energy. If frequency is increased, you increase intensity by changing the pitch of the sound. So, you're right in that if you increase amp and freq, you increase intensity but since the question specifically asks about what would happen if the dB level increases (suggesting loudness), I would go with amplitude.

Hope that helps!