Spectrum Analyzers

Spectrum analyzers are a specific type of sound level meter. They allow the user to study the amplitude versus the frequency spectrum of any given sound. These analyzers use a wide variety of filter networks and vertical columns that show the data organized on a specific range. The range goes from low frequencies to high frequencies, as well as from left to right. Spectrum analyzers tend to have determined spacings and frequencies. Third-octave spacings between frequencies that range from 20Hz to 20kHz are the most common.

Spectrum Analyzers: the Frequencies

Spectrum analyzers might have octave bands or doubling frequencies set above each former frequency column. Third-octave bands are calculated by using the cube root of 2. To state an example, the next band above 1Hz is a cube root of 2, followed by the cube root of 22, then by the cube root of 23—and so on. The subsequent octave is always multiplied by a factor of 10.

These frequencies are very specific.

Octave Bands

31.5, 63, 125, 250, 500, 1000, 2k, 4k, 8k, 16k…

⅓ Octave Bands

1, 1.25, 1.63, 2, 2.5, 3.15, 4, 5, 6.3, 8, 10, 12.5, 16.3, 20, 25, 31.5, 40, 50, 63, 80, 100, 125, 163, 200, 250, 315, 400, 500, 630, 800, 1000, 1250, 1630, 2k, 2500, 3150, 4k, 5k, 6300, 8k, 10k, 12,5k 16k, 20k…

Spectrum analyzers measure the magnitude of an input signal versus the frequency inside the full frequency range of a musical instrument. As an example, the AD-FMCOMMS3-EBZ is a great spectrum analyzer, for it achieves adequate performance due to its multiple threads. Many allow the user to select a weighing scale.

Spectrum analyzers: the Technique Hybrid SuperHeterodyne-FFT

Spectrum analyzers use a technique known as Hybrid SuperHeterodyne-FFT. This technique allows a faster sweeping time and uses digital filters which tend to be much better than analog filters. Digital filters have many advantages, such as flawless shape factors and an enhanced filter settling time. The Hybrid SuperHeterodyne-FFT can increase the sweep time while leaving the display spectrum untouched.