This paper presents a design procedure for structural health monitoring systems based on bulk wave ultrasonic sensors for structures fabricated from polycrystalline materials. When designing a monitoring system, maximum coverage pertransducer is a general requirement in order for the system to be economic. For coarse grained polycrystalline materials,monitoring is often made challenging by low signal to noise ratios caused by grain scattering. Therefore, when designing a monitoring system for these materials, in addition to the economic requirement, it needs to be ensured that an adequate signal to noise ratio can be obtained throughout the monitoring volume. This typically introduces a trade-off between volume coverage per transducer and sensitivity that must be investigated. In this paper, this trade-off is studied and a methodology using signal to noise maps is presented to design the system, i.e. choose the optimal transducer parameters and placement. Firstly, a combined analytical-and-numerical approach is used to generate a signal to noise map. Then, the influence of various factors on signal to noise ratio is investigated. Finally, two representative examples,with different criteria, are given to illustrate the methodology. In one example, the full surface area of the test piece is covered with transducers and the optimum gives the deepest coverage. The other one aims to achieve the minimum fractional surface area that has to be covered with transducers to monitor a narrow depth range far from the surface,which has a potential application in weld monitoring. Results show that the optimum is likely to be at much lower frequency than typically used in inspection, as tracking signals with time gives sensitivity gains. Experiments were carried out to illustrate that higher volume coverage can be obtained at lower frequencies.