Piezoelectrets (also known as ferroelectrets) are a kind of cellular electret material with strong piezoelectric effect. Such materials exhibit flexibility, low density and small acoustic impedance. Therefore, piezoelectrets are ideal materials for air-borne flexible sound transducers. Aiming at sound transducers with high sensitivity and thermal stability, in this paper, laminated fluorinated polyethylene propylene (FEP) and polytetrafluoroethylene piezoelectret films with a regular cellular microstructure are prepared by a procedure involving template-based cellular structure formation and polarization. The results show that the characteristic acoustic impedance of such laminated FEP/PTFE films is 0.02 MRayl. The quasi-static piezoelectric charge coefficient d33 up to 800 PC/N is achieved in a small applied pressure range. The maximum value of sensitivity of the microphones based on laminated FEP/PTFE piezoelectrets films, up to 6.4mV/Pa at 1 kHz, is achieved. Besides, the frequency response curve of the device is flat in the whole audio range. For an ultrasonic transmitter with a diameter of 20 mm and driven by a voltage of 600 V (Vpp), the sound pressure level (SPL) generated by it increases from 80 to 90 dB (Ref. 20 μPA) as increasing frequency from 40 to 80 kHz. The thermal stability of the sensitivity for the transducers made of such laminated FEP/PTFE piezoelectret films is much superior to that of polypropylene (PP) piezoelectret based devices. The sensitivity of the present studied devices remains 26% of the initial value after an annealing treatment at 125 OC for 211 h. The improved thermal stability is attributed to the excellent space charge storage stability of FEP and PTFE.