Cleanline installations

Blind-source separation approaches such as ICA may help mitigate line noise, but often fail to completely remove the noise due to spatiotemporal non-stationarities in the noise.

In brief, the data is traversed by a sliding window. Within each window, the signal is transformed to the frequency domain using a multi-taper FFT. The complex amplitude amplitude and phase is thus obtained for each frequency. Under the assumption of a deterministic sinusoid embedded in white noise, we can set up a regression of the multi-taper transform spectrum of this sinusoidal signal onto the multitaper spectrum of the original data at a given frequency.

The regression coefficient is a complex number representing the complex amplitude phase and amplitude of the deterministic sinusoid. From this, a time-domain representation of the sinusoid may be constructed and subtracted from the data to remove the line. Typically, one does not know the exact line frequency. For instance, in the U. To ameliorate this problem a Thompson F-Test may be applied to determine the statistical significance of a non-zero coefficient in the above regression indicating a sinusoid with significantly non-zero amplitude.

We can then search within a narrow band around the expected location of the line for the frequency which maximizes this F-statistic above a significance threshold e. Overlapping short e. The discontinuity at the point of window overlap can be smoothed using a sigmoidal function. The example below demonstrates such a function for different smoothing factors slope of the sigmoid.

CleanLine allows you to specify the multi-taper frequency resolution by the 'Bandwidth' parameter. This is the width of a peak in the spectrum for a sinusoid at given frequency. Due to the time-frequency uncertainty principle, decreasing bandwidth increases the necessary length of the sliding window in order to obtain a reasonable frequency decomposition. CleanLine fixes T to be the sliding window length, so W Bandwidth is the only required parameter.

If the 'Verbosity' option is set to 1, then CleanLine will display the multi-taper parameters in the command line on execution of the function. If you have multiple epochs you need to make sure that your window size and step size exactly divides the epoch length.

In other words, you do not want any sliding windows to overlap two epochs since line noise phase and amplitude may shift at that point, making it impossible to perform the time-domain line subtraction. If you have relatively short epochs e. In this way, the lines are estimated and removed for each epoch individually.

When using the GUI, the default values for window length and step size are automatically set to the epoch length. If you don't care to see the visualize the final results of the cleaning operation, you may also wish to set 'ComputeSpectralPower',false which will speed up computation considerably. As such, this defines the multi-taper frequency resolution. If channels are cleaned, ICA activations are reconstructed based on clean channels.

SlidingWinLength: Sliding window length sec Default is the epoch length. Accept analytics cookies Reject analytics cookies View cookies. Hide this message. Cookies on Companies House services We use cookies to make our services work and collect analytics information. Skip to main content. Companies House does not verify the accuracy of the information filed link opens a new window. Follow this company File for this company. Company status Active. Company type Private limited Company Incorporated on 24 November Accounts Next accounts made up to 30 November due by 31 August Last accounts made up to 30 November Confirmation statement Next statement date 24 November due by 8 December Last statement dated 24 November