Optimization of double-layer sound absorber in a broadband frequency range using transfer matrix method and Evolution Strategies algorithm

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Table 4

The optimized parameters and the corresponding average absorption coefficients.

	Single layer					Double layer

Optimized for	P	d	R	L	α	P₁	P₂	d₁	d₂	rt₁	rt₂	R₂	R₁	L₁	α
									Foam
100 Hz–800 Hz	0.012	0.015	16538	0.085	0.788	35.0%	1.4%	0.01	0.015	0.035	0.831	13618	8315.7	0.045	0.8037
800 Hz–1600 Hz	0.43	0.014	7444	0.073	0.984	38.2%	18.9%	0.015	0.01	0.035	0.831	12947	40309	0.045	0.9988
1600 Hz–3000 Hz	0.221	0.015	7243	0.085	0.986	46.0%	23.0%	0.01	0.01	0.035	0.831	9205.8	28176	0.0234	0.9994
									Fiber
100 Hz–800 Hz	0.021	0.015	19752	0.038	0.809	42.0%	2.1%	0.01	0.015	0.035	0.831	7799.6	15494	0.045	0.8121
800 Hz–1600 Hz	0.176	0.006	8158	0.071	0.985	38.2%	18.9%	0.015	0.01	0.035	0.831	12947	40309	0.045	0.9988
1600Hz–3000 Hz	0.199	0.015	10025	0.085	0.991	28.0%	32.0%	0.014	0.01	0.035	0.831	8709.1	43342	0.0189	0.9996
									Polyester
100 Hz–800 Hz	0.02	0.015	23138	0.085	0.831	28.5%	1.9%	0.01	0.01	0.035	0.831	13075	8381	0.045	0.8224
800 Hz–1600 Hz	0.28	0.015	16538	0.058	0.984	26.5%	12.0%	0.015	0.01	0.035	0.831	10193	37900	0.041	0.9983
1600 Hz–3000 Hz	0.182	0.015	17286	0.085	0.991	14.1%	27.7%	0.015	0.015	0.035	0.831	10241	12741	0.0234	0.9891

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