This paper presents the existence of a double-negative acoustic metamaterial, where both the effective density and bulk modulus are simultaneously negative. This system is an acoustic analog of Veselago's electromagnetic medium, which also exhibits a negative refractive index. The double negativity in acoustics arises from low-frequency resonances, similar to the case in electromagnetism, but the negative density and modulus are derived from a single resonance structure, unlike in electromagnetism where negative permittivity and permeability come from different mechanisms. The authors demonstrate that it is mathematically possible to achieve a double-negative acoustic medium by dispersing soft rubber in water. Unlike electromagnetic metamaterials, natural materials do not inherently have negative density or bulk modulus. However, through low-frequency resonances, the effective bulk modulus and density can become negative. The effective medium theory is used to calculate these parameters, and the results show that both the effective bulk modulus and density can be negative in a narrow frequency range. The paper also shows that the double-negative acoustic medium can exhibit negative refraction, similar to Veselago's medium. The results are validated using multiple-scattering methods and effective medium approximations. The study highlights that the double-negative band arises from resonances, not from Bragg scattering. The findings demonstrate that acoustic metamaterials can be designed to have unique properties such as negative refraction and subwavelength focusing. The research is supported by the RGC Hong Kong and acknowledges the contributions of other researchers.This paper presents the existence of a double-negative acoustic metamaterial, where both the effective density and bulk modulus are simultaneously negative. This system is an acoustic analog of Veselago's electromagnetic medium, which also exhibits a negative refractive index. The double negativity in acoustics arises from low-frequency resonances, similar to the case in electromagnetism, but the negative density and modulus are derived from a single resonance structure, unlike in electromagnetism where negative permittivity and permeability come from different mechanisms. The authors demonstrate that it is mathematically possible to achieve a double-negative acoustic medium by dispersing soft rubber in water. Unlike electromagnetic metamaterials, natural materials do not inherently have negative density or bulk modulus. However, through low-frequency resonances, the effective bulk modulus and density can become negative. The effective medium theory is used to calculate these parameters, and the results show that both the effective bulk modulus and density can be negative in a narrow frequency range. The paper also shows that the double-negative acoustic medium can exhibit negative refraction, similar to Veselago's medium. The results are validated using multiple-scattering methods and effective medium approximations. The study highlights that the double-negative band arises from resonances, not from Bragg scattering. The findings demonstrate that acoustic metamaterials can be designed to have unique properties such as negative refraction and subwavelength focusing. The research is supported by the RGC Hong Kong and acknowledges the contributions of other researchers.