A Direct Measurement of Inter-Element Cross-Talk in Ultrasound Arrays

In a transducer array, spurious vibration modes generate waves propagating in the backing material, in the kerf-filler, and in the lens leading to coupled resonance of neighboring elements. It has been shown that this inter-element cross-talk may be responsible for significant distortion of the field radiated by an array, especially when large steering angles are applied. In a previous study we indirectly estimated the cross-talk by fitting one-way field measurements to simulations including an elementary cross-talk model. In this work, we present a method to directly measure and characterize the inter-element cross-talk in an array of transducers. Three array types (phased, linear and convex) were coupled to water and tested in connection to a Vantage 256 system (Verasonics). The cross-talk was estimated for different transmission amplitudes, in the range 3-45 V. Results highlight that the cross-talk on neighboring elements decays exponentially with distance from the transmitting element, while, as expected, the propagation delay linearly increases. The average cross-talk decay rate was 3.5, 3.6, 8.9 dB/pitch, while the propagation speed of the spurious wave was 921, 937, 815 m/s for phased, linear, and convex arrays, respectively.