Local adjustment of SNR

To enable the local adjustment of SNR, you need to enable the corresponding snr_mode when initializing the SourceSimulator class:

from meegsim.simulate import SourceSimulator

# src should be loaded or created beforehand
sim = SourceSimulator(src, snr_mode="local")

For the local adjustment of SNR, we calculate the mean variance of each point or patch source across all sensors and adjust it relative to the mean variance of all noise sources (mean over sensors but summed over noise sources). The calculation of variance is performed after filtering both time series (signal and noise) in the frequency band of interest.

Note

For the adjustment of SNR, you always need to add noise sources to the simulation.

By default, no adjustment of local SNR is performed. To enable it, you need to specify the value of SNR using the snr argument and provide the limits of the frequency band in snr_params when adding the point or patch sources:

import numpy as np

# add some noise sources
sim.add_noise_sources(
    location=select_random,
    location_params=dict(n=10)
)

# now add point sources with adjustment of SNR
sim.add_point_sources(
    location=[(0, 123), (0, 456), (1, 789)],
    waveform=np.ones((3, 1000)),
    snr=5,
    snr_params=dict(fmin=8, fmax=12),
    ...
)

It is also possible to specify SNR for each of the sources separately by providing one value for each source:

import numpy as np

# add some noise sources first
sim.add_noise_sources(
    location=select_random,
    location_params=dict(n=10)
)

# now add point sources with adjustment of SNR
sim.add_point_sources(
    location=[(0, 123), (0, 456), (1, 789)],
    waveform=np.ones((3, 1000)),
    snr=[1, 2.5, 5],
    snr_params=dict(fmin=8, fmax=12),
    ...
)