Multi-channel FFT Spectrum Analyzer Tool
Features
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User-friendly Frequencies: Traditional FFT-based spectrum analyzers use FFT's (Fast Fourier Transforms) with lengths that are powers of 2 (e.g. 2 to the 12th power = 4096). With typical audio sample rates, such as 48 kHz, this yields non-integer (awkward) frequency resolutions, such as 11.71875 Hz (48000/4096 = 11.71875). SignalScope's FFT Analyzer uses mixed-radix FFT's that yield frequency resolutions that are more than just user-friendly—they allow for precise amplitude measurement at frequencies such as 1000 Hz (a frequency commonly used for calibrating sound level meters and measuring total harmonic distortion, or THD). For example, an FFT length of 4800, when used with a sample rate of 48 kHz, yields a frequency resolution of exactly 10 Hz (48000/4800 = 10).
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Multi-channel Display: View live spectra from up to 16 channels (8 channels on iPhone), simultaneously, including output channels.
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Save Data: Export spectrum magnitude values and metadata to a data file (.csv, .mat, or .txt). Or, generate a high-resolution image of the graph and save it to a PDF file.
Specifications
  • Input: Up to 16 channels simultaneously (limited to 8 on iPhone), selected from any available input, output, or virtual output channels
  • FFT Type: Mixed Radix
  • Frequency Resolution (Hz), per sample rate:
    • Built-in Accelerometer (iPhone and iPad), 100 Hz
      • 10, 5, 2, 1, 0.5, 0.2, 0.1
    • 11025 Hz
      • 0.5, 0.2, 0.1
    • 12000 Hz
      • 50, 40, 20, 16, 10, 8, 5, 4, 2, 1, 0.5, 0.2, 0.1
    • 22050 Hz
      • 5, 1, 0.5, 0.2, 0.1
    • 44100 Hz
      • 50, 10, 5, 2, 1, 0.5, 0.2, 0.1
    • 88200 Hz
      • 50, 10, 5, 4, 2, 1, 0.5, 0.2, 0.1
    • 176400 Hz
      • 50, 10, 8, 5, 4, 2, 1, 0.5, 0.2, 0.1
    • All other sample rates
      • 50, 40, 32, 20, 16, 10, 8, 5, 4, 2, 1, 0.5, 0.2, 0.1
  • FFT Length: Set automatically, based on frequency resolution and current sample rate (e.g. at 48 kHz, a frequency resolution of 5 Hz requires an FFT length of 9600 points)
  • Data Windows:
    • Uniform (rectangular)
    • Bartlett
    • Blackman
    • Flat Top
    • Hamming
    • Hann
    • Rife-Vincent 2
    • Exponential Decay
    • Force
    • Force Exponential
    • Exponential Decay Window: User defined time constant and final value
    • Force Window: User defined window length in seconds or percent
    • Window Preview: In-menu graph of the window shape
  • Overlap (%): Off (0), 50, 75, 80, 90, Max (automatically calculated, limited to approximately 20 FFT calculations per second)
  • Frequency Weighting: Z (zero, or no weighting), A, C
  • Averaging: Off, Linear (Stable), Exponential, Peak Hold
  • Visible Frequency Limits: Min/Max, User-adjustable between 0 and Nyquist
  • Vibration Unit Conversion: Acceleration, Velocity, Displacement
  • Scale
    • Horizontal divisions: 10 (linear frequency scale)
    • Vertical divisions: 10
    • Autoscale: Off, Auto, Up, Down
    • Vertical Axis: Lin, Log, dB
    • dB Magnitude Scale (dB/Div)
      • 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.08, 0.09, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.8, 0.9, 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 8.0, 9.0, 10.0, 12.0, 15.0, 16.0, 18.0, 20.0, 24.0, 25.0, 27.0, 30.0
    • Lin/Log Magnitude Scale (Units/Div)
      • 1e-9, 2e-9, 3e-9, 4e-9, 5e-9, 6e-9, 8e-9, 10e-9, 20e-9, 30e-9, 40e-9, 50e-9, 60e-9, 80e-9, 100e-9, 200e-9, 300e-9, 400e-9, 500e-9, 600e-9, 800e-9, 1e-6, 2e-6, 3e-6, 4e-6, 5e-6, 6e-6, 8e-6, 10e-6, 20e-6, 30e-6, 40e-6, 50e-6, 60e-6, 80e-6, 100e-6, 200e-6, 300e-6, 400e-6, 500e-6, 600e-6, 800e-6, 1e-3, 2e-3, 3e-3, 4e-3, 5e-3, 6e-3, 8e-3,10e-3, 20e-3, 30e-3, 40e-3, 50e-3, 60e-3, 80e-3,100e-3, 200e-3, 300e-3, 400e-3, 500e-3, 600e-3, 800e-3, 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 8.0, 10.0, 20.0, 30.0, 40.0, 50.0, 60.0, 80.0, 100.0, 200.0, 300.0, 400.0, 500.0, 600.0, 800.0, 1e3, 2e3, 3e3, 4e3, 5e3, 6e3, 8e3, 10e3, 20e3, 30e3, 40e3, 50e3, 60e3, 80e3, 100e3, 200e3, 300e3, 400e3, 500e3, 600e3, 800e3
    • Level Type: peak, peak-to-peak, rms
    • Horizontal Axis (Frequency Scale): Lin, Log
    • Frequency Units: Hz, cpm
  • Spectral Smoothing: Enable/Disable (requires logarithmic frequency scale)
    • Smooth Bandwidth (fractional octave bandwidth): 1/6, 1/12, 1/24
    • Smoothing Type: Avg, Max, Min
  • Cursor
    • Harmonic Cursors: up to 128
    • Horizontal Bar: Hidden or drawn at the instantaneous amplitude of any available waveform
    • Peak Track: Off, Max, Min
      • The cursor can track the peak value of any channel which has been selected for analysis
  • Triggering: Enable/Disable
    • Channel selection: Self or any available input or output channel
    • Mode: Auto, Normal, Single
    • Slope: Positive, Negative
    • Threshold
  • Data Export
    • Data File Format: CSV, MAT, TXT
    • Image: PDF
    • Optionally include current location in exported data files.
    • Option to export only visible frequencies.
  • Data Import
    • Data File Format: CSV, MAT, TXT (only files created by the FFT Analyzer tool)
    • The total number of loaded static spectra and live spectra cannot exceed 16 (8 on iPhone)
    • Trace Opacity: 0.25 - 1.0
    • Trace Thickness: 1, 2, 3
  • Average Curve (Pro Feature)
    • The total number of loaded static spectra (including average curves) and live spectra cannot exceed 16 (8 on iPhone)
    • Max Data Files Per Average Curve: 999999999
    • Data File Format: CSV, MAT, TXT (only files created by the FFT Analyzer tool)
  • Specifications Subject to Change
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