A piezoelectric micromachined ultrasonic transducer (pMUT) array, comprising: a plurality of drive/sense electrode rails disposed over an area of a substrate and electrically addressable independently; and a plurality of piezoelectric transducer element populations (110A-110L, 120A-120L) comprising a first population of transducer elements and a second population of transducer elements , wherein drive/sense electrodes of the transducer elements within a piezoelectric transducer element population are coupled to a same respective one of the drive/sense electrode rails, characterized in that an electromechanical coupling (C1) between the transducer elements of the first population and the second population is less than an electromechanical coupling (C2) between two adjacent transducer elements within a piezoelectric transducer element population, and wherein each of the plurality of piezoelectric transducer element populations is configured to provide a plurality of separate but overlapping frequency responses, wherein the electromechanical coupling between the transducer elements within the piezoelectric transducer element population is sufficient to induce at least one degenerate mode, the at least one degenerate mode having a degenerate resonant frequency (fn2) split from a natural resonant frequency (fn1) of an individual piezoelectric transducer element in the piezoelectric transducer element population, wherein two or more of a distance (Py), the elastic modulus of a material, or a cross-sectional coupling area of a first region between the transducer elements within the first population is different than a corresponding one of the distance (Px), the elastic modulus of the material, or the cross-sectional coupling area of a second region between the transducer elements of the first population and the second population . a plurality of drive/sense electrode rails disposed over an area of a substrate and electrically addressable independently; and a plurality of piezoelectric transducer element populations (110A-110L, 120A-120L) comprising a first population of transducer elements and a second population of transducer elements , wherein drive/sense electrodes of the transducer elements within a piezoelectric transducer element population are coupled to a same respective one of the drive/sense electrode rails, characterized in that an electromechanical coupling (C1) between the transducer elements of the first population and the second population is less than an electromechanical coupling (C2) between two adjacent transducer elements within a piezoelectric transducer element population, and wherein each of the plurality of piezoelectric transducer element populations is configured to provide a plurality of separate but overlapping frequency responses, wherein the electromechanical coupling between the transducer elements within the piezoelectric transducer element population is sufficient to induce at least one degenerate mode, the at least one degenerate mode having a degenerate resonant frequency (fn2) split from a natural resonant frequency (fn1) of an individual piezoelectric transducer element in the piezoelectric transducer element population, wherein two or more of a distance (Py), the elastic modulus of a material, or a cross-sectional coupling area of a first region between the transducer elements within the first population is different than a corresponding one of the distance (Px), the elastic modulus of the material, or the cross-sectional coupling area of a second region between the transducer elements of the first population and the second population . <EOS>