Question 1

What is a spectrogram?

Accepted Answer

A spectrogram is a color map of sound. Time runs from left to right, frequency runs from low at the bottom to high at the top, and the colors show how strong each frequency is at each moment. It lets you see parts of a recording that a waveform alone does not show.

Question 2

How is a spectrogram different from a waveform?

Accepted Answer

A waveform shows how the overall signal level changes over time. A spectrogram breaks the signal into frequencies and shows how the strength of those frequencies changes over time. The waveform is useful for seeing timing and loudness; the spectrogram is useful for seeing pitch, tones, noise, and frequency limits.

Question 3

How do I read the colors and frequency labels?

Accepted Answer

Brighter colors represent stronger frequency content, while darker areas represent weaker or absent content. The labels on the left show frequency in hertz (Hz) or kilohertz (kHz). Low sounds appear near the bottom and high sounds appear near the top.

Question 4

What can I look for in a spectrogram?

Accepted Answer

You can look for steady tones, low-frequency hum, broadband hiss, silent sections, and sharp frequency cutoffs. A horizontal line can indicate a sustained tone, while energy spread across many frequencies can indicate noise or a complex sound.

Question 5

Which frequency scale should I choose?

Accepted Answer

Mel is a hearing-oriented scale and is a useful default for speech, music, and general listening. Linear spaces frequencies evenly, which is useful when you want to compare exact frequency intervals. Logarithmic gives more visual space to lower frequencies and less to higher frequencies.

Question 6

What does the resolution setting change?

Accepted Answer

The setting changes the FFT window used to calculate the spectrogram. A larger value can separate nearby frequencies more clearly, but it takes more processing and represents a longer slice of audio at once. A smaller value is quicker and preserves changes over short periods more clearly. The default is 1024.

Question 7

Why can the spectrogram take a few seconds to appear?

Accepted Answer

The browser first decodes the audio and then analyzes it in many short windows to calculate the frequencies shown in the spectrogram. Longer files and higher resolution settings require more calculations. The loading message remains visible until the spectrogram has been drawn.

Question 8

Which audio files can I view?

Accepted Answer

You can select an audio file that your browser can decode. Format support can vary by browser and operating system, so a file that plays in one browser may not open in another.

Question 9

Can a spectrogram prove that a file is lossless or high quality?

Accepted Answer

No. A spectrogram can reveal clues such as a sharp frequency cutoff, strong noise, or empty high-frequency regions, but those patterns do not prove the file's source or overall quality. This tool displays the frequency data for you to inspect; it does not automatically grade or authenticate the recording.

Audio spectrogram viewer

How to read a spectrogram

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