How to understand low frequency and high frequency?
Low frequency generally refers to frequencies below 20 Hz , while high frequency refers to frequencies above 20 kHz .
Low frequency and high frequency refer to the frequency of the signal. Frequency refers to the number of times a signal repeats per unit time, usually in Hertz (Hz). The higher the frequency, the more times the signal repeats per unit time.
In EMG signals , the division of low frequency and high frequency usually depends on specific research or application requirements. Generally speaking, low-frequency signals in EMG signals often refer to signals with a frequency below 1 Hz , while high-frequency signals refer to signals with a frequency above 10 Hz.
Low-frequency EMG signals are usually related to the basic activities of muscles , such as maintaining muscle tension, posture maintenance and other
high-frequency signals are usually related to rapid muscle contraction and movement , such as muscle contraction and relaxation, signals at the beginning and end of movement, etc.
In the research and application of EMG, low-frequency and high-frequency signals can be used to identify and quantify the characteristics of muscle activity, such as muscle fatigue, coordination, etc. The analysis of low-frequency and high-frequency signals can provide information about muscle activity, thereby helping people to better understand and control muscle activity, as well as applications in rehabilitation, sports training and other fields.
How to understand low frequency noise?
Low-frequency noise refers to noise signals with lower frequencies.
In the field of acoustics, low-frequency noise is generally defined as acoustic signals with frequencies below 20 Hz , which are generally considered inaudible.
Low frequency noise can come from a variety of sources such as electronic equipment, machinery running, wind, ocean waves , etc. These noise signals may affect human physical and psychological health, especially in the case of long-term exposure. Therefore, in some environmental and industrial applications, measures need to be taken to reduce the generation and propagation of low-frequency noise to protect human health and safety.
How to eliminate low frequency noise in EMG signal?
1. Use a high-pass filter to filter out low-frequency components and retain high-frequency components. Commonly used high-pass filters include Butterworth filters, Butterworth filters, and the like.
2. Adaptive filtering : This filtering method can automatically adjust the parameters of the filter to adapt to changes in the signal. The design of adaptive filter is usually based on LMS algorithm, RBF algorithm and so on.
3. Peak detection : By performing peak detection on the signal , high-frequency components can be identified, thereby filtering out low-frequency noise. Peak detection methods include absolute peak detection, relative peak detection, and the like.
4. Window function : In signal analysis, window functions are often used to reduce spectrum leakage and noise interference. The selection of the window function is usually based on the nature of the signal and the analysis requirements. Commonly used window functions include Hamming window, Haining window, etc.