Apparatus and methods for acoustically isolating logging tool receiver and transmitter sections. One or more modular isolators is arranged between the receiver and transmitter sections. The modular isolators comprise a high tensile strength while also providing for a high wave attenuation level. The modular isolators are mechanical mass-spring systems capable of absorbing acoustic waves propagating along the logging tool. The mass is a swinging sleeve, and the spring includes a Belleville spring stack. The use of the strong modular isolators provides acoustic isolation between the transmitters and receivers for the complete sonic frequency band at multiple modes.