Type I bursts are radiation spikes that last around one second and occur over a relatively narrow frequency range ( Δ Δ f / f ≈ ≈ 0.025 ) with little-to-no discernible drift in frequency. They tend to occur in groups called noise storms that are often superimposed on enhanced continuum (broad-spectrum) emission with the same frequency range. While each individual Type I burst does not drift in frequency, a chain of Type I bursts in a noise storm may slowly drift from higher to lower frequencies over a few minutes. Noise storms can last from hours to weeks, and they are generally observed at relatively low frequencies between around 50 and 500 MHz.