_applied sciences_  
_Article_  
**Noise Characteristics Analysis of Medical Electric Leg**  
**Compression Machine Using Multibody Dynamic Simulation**  
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In the EECP procedure, a patient lies on the bed wearing cuffs on the legs at the calves and thighs, and buttocks (or upper thighs). The cuffs are inflated during diastole, applying external pressure on the body, and deflated during systole, releasing the applied pressure.  
The timing of sequential inflation and deflation is synchronized with the cardiac cycle. During diastole, the pressure exerted by the cuffs facilitates the blood flow from the legs to the upper body; during systole, the blood flow to the lower body increases as the cuffs deflate, strengthening the myocardium and facilitating new blood vessel formation. With these benefits alone, EECP can have therapeutic effects on patients with angina or myocardial infarction [1; 2; 3; 4; 5]. Furthermore, the therapeutic effects of EECP include vascular endothelial cell activation, aging prevention through enhanced blood circulation and oxygen supply, increased blood flow to the brain and kidneys, blood vessel regeneration, toxins, blood plaque clearance, and regeneration of new blood vessels [6].  
A typical EECP treatment consisting of 35 one-hour sessions (five days a week over seven weeks) can increase blood flow around clogged blood vessels by activating the surrounding dormant blood vessels [7]. Based on these benefits, EECP treatment is recommended for cases where medical or surgical treatments cannot be considered [8]. As shown in Figure 1, traditional EECP treatment uses a pneumatic system where two to three air compressors are placed under the bed. Compressed air is instantaneously injected into the cuffs wrapped around the patient's legs during the diastole phase of the patient's cardiac cycle.  
Since its initial development in the 1960s, EECP technology has not seen much progress [9].  
The machine tends to generate operational noise and heat, and physical impact on the patient's body, but the technology to address these issues has not yet been developed. The operational noise causes discomfort to both patients and medical staff, and persistent exposure to this noise can cause noise-induced hearing loss.  
In this study, an electric EECP machine was developed to overcome the shortcomings (noise and shocks on the body) of conventional EECP machines. In general, hospital noise levels need to be controlled and limited to 50 dB or lower to prevent the noise from discomforting and disturbing other patients [10; 11; 12; 13; 14].  
By replacing the air compressors with electrical motors, the disturbing noise and physical impact on the body were resolved. In addition, the motors can be electronically controlled for each compression target (c valves, thighs, buttocks), which means that the compression timings and pressures can be set individually. This capability is essential for the development of a treatment scheme that is optimized for the patient's cardiac state and cuff locations.  
Since the effect of each cuff on the blood flow can be analyzed, the cuff locations, number of cuffs, and compression timing in relation to other cuffs can be fine-tuned for each patient to achieve the maximum EECP effect. By removing the air compressors, a core component of the pneumatic system, the electric leg compression machine developed  
Figure 1: Pneumatic EECP therapy device.  
in this study, was designed to produce lower levels of operating noise and to allow easy transportation of the entire machine, as shown in Figure 2.  
In the new electric leg compression machine, electrical motors, replacing the air compressors, apply pressure on the legs by repeatedly inflating and deflating the cuffs. The motors need to repeat clockwise and counter-clockwise rotations in a short period, and accordingly, the gears should mesh and rotate.