An ultrasonic measurement device for detecting a measurement variable of a medium located in a measurement chamber comprising: The measurement chamber with a measurement chamber wall and a measurement chamber longitudinal axis; at least one pair of ultrasonic transducers (21, 22), which is arranged on a first measurement chamber side (13.1) of the measurement chamber, wherein the ultrasonic transducers of a pair are designed to send ultrasonic signals along an ultrasonic signal path between the ultrasonic transducers of the pair through the volume of the measurement chamber and to receive ultrasonic signals, the ultrasonic signals having a central frequency, an ultrasonic signal path through the volume of the measurement chamber in each case comprising at least one ultrasonic signal reflection on at least one reflection surface (15.1), a reflection surface being arranged on a measurement chamber inner surface of the measurement chamber wall lying opposite the first measurement chamber side (13.1); an electronic measurement/operating circuit which is designed to operate the ultrasonic transducers and to evaluate measurement signals generated by means of the ultrasonic transducers and to provide measurement values of measurement variables, the measurement chamber wall being designed, in the area of the reflection surface opposite first measurement chamber side, at least to hinder a reflection of an ultrasonic signal on a measurement chamber outer surface (11.1) of the measurement chamber wall in the direction of the ultrasonic signal path, the measurement chamber wall having, in the area of the reflection surface, a maximum wall thickness which is greater by at least a factor of 1.5 and in particular at least a factor of 2 and preferably at least a factor of 2.5 than a Rayleigh wavelength of the ultrasonic signal belonging to the central frequency in the measurement chamber wall, wherein the measurement chamber outer surface (11.1) has, in the area of the reflection surface, at least one indentation parallel to the measurement chamber longitudinal axis, wherein indentation surfaces (30.3) are non-parallel to the reflection surface, the indentation surfaces being designed to reflect ultrasound entering the measurement chamber wall laterally away, an entirety (30.1) of the at least one indentation having a width (30.2) which corresponds at least to a width of the reflection surface multiplied by a factor F1, F1 being greater than 0.7 and in particular greater than 0.8 and preferably greater than 0.9. The measurement chamber with a measurement chamber wall and a measurement chamber longitudinal axis; at least one pair of ultrasonic transducers (21, 22), which is arranged on a first measurement chamber side (13.1) of the measurement chamber, wherein the ultrasonic transducers of a pair are designed to send ultrasonic signals along an ultrasonic signal path between the ultrasonic transducers of the pair through the volume of the measurement chamber and to receive ultrasonic signals, the ultrasonic signals having a central frequency, an ultrasonic signal path through the volume of the measurement chamber in each case comprising at least one ultrasonic signal reflection on at least one reflection surface (15.1), a reflection surface being arranged on a measurement chamber inner surface of the measurement chamber wall lying opposite the first measurement chamber side (13.1); an electronic measurement/operating circuit which is designed to operate the ultrasonic transducers and to evaluate measurement signals generated by means of the ultrasonic transducers and to provide measurement values of measurement variables, the measurement chamber wall being designed, in the area of the reflection surface opposite first measurement chamber side, at least to hinder a reflection of an ultrasonic signal on a measurement chamber outer surface (11.1) of the measurement chamber wall in the direction of the ultrasonic signal path, the measurement chamber wall having, in the area of the reflection surface, a maximum wall thickness which is greater by at least a factor of 1.5 and in particular at least a factor of 2 and preferably at least a factor of 2.5 than a Rayleigh wavelength of the ultrasonic signal belonging to the central frequency in the measurement chamber wall, wherein the measurement chamber outer surface (11.1) has, in the area of the reflection surface, at least one indentation parallel to the measurement chamber longitudinal axis, wherein indentation surfaces (30.3) are non-parallel to the reflection surface, the indentation surfaces being designed to reflect ultrasound entering the measurement chamber wall laterally away, an entirety (30.1) of the at least one indentation having a width (30.2) which corresponds at least to a width of the reflection surface multiplied by a factor F1, F1 being greater than 0.7 and in particular greater than 0.8 and preferably greater than 0.9.