This lesson is for week 1 of Introduction To Music Production at Coursera.org. I will be teaching how microphones affect voice timbre using two common microphones.
The gear I will be using for this demonstration is:
- A Shure SM58 microphone + Blue Icicle microphone converter
- An iPhone 4S built-in microphone
- A MacBook Air computer
- Sonic Visualizer application
I recorded myself singing the English vowels “a, e, i, o, and u” at C#3 (pitch) on both my Shure mic and my iPhone mic. I held them the same distance from my mouth and pointed them both in the direction of my face.
Hear is the Shure recording, and spectrograph analysis:
And here is the iPhone internal mic recording and spectrogram:
I picked this color scheme on the spectrograph for its high contrast, but my apologies if the screenshot is difficult to make out. The x-axis represents time elapsed, y represents the frequencies in Hertz, and z is the amplitude of the sounds.
The pitch C#3, if it’s perfect, has a fundamental (lowest frequency) at exactly 138.591 Hertz. What I sang is a complex tone that has a unique timbre—the sound is comprised of a series of sine waves (fundamental and harmonics) with unique frequencies (pitch levels) and amplitudes (in short, loudness) that change over time.
We see on the Shure spectrograph that the bottom-most frequency for all notes (a, e, i, o, and u in that order) is around 139 for C#3 while there are rather strong harmonics for all vowels around G#4, an octave and a fifth above the fundamental. The largest frequency range is seen in “i” and the smallest range in “u.” Any gaps in frequency range gradiate rather subtly for a smooth blended timbre.
On the iPhone spectrograph, we see that each vowel contains many more frequencies and we’re losing that nice tapering of the sound into the higher range. The gaps in the range are more pronounced, which breaks up the timbre causing a slightly cruder overall sound.
This analysis was interesting for me in that it makes me think more about how the subtleties captured by a nice mic will enhance a sound. It’s common knowledge that an iPhone built-in mic is not as high quality as most external mics, but I never had an idea of why until now. Thanks for reading!