Voice recognition module SEN0539 connecting to Arduino Nano

Hi, I'm having real problems connecting this device to my Nano.

With the original programming 
#if (defined(ARDUINO_AVR_UNO) || defined(ESP8266))  // Use software serial

SoftwareSerial softSerial(/*rx =*/4, /*tx =*/5);

DFRobot_DF2301Q_UART asr(/*softSerial =*/&softSerial);

#elif defined(ESP32)  // Use the hardware serial with remappable pin: Serial1

DFRobot_DF2301Q_UART asr(/*hardSerial =*/&Serial1, /*rx =*/D3, /*tx =*/D2);

#else                 // Use hardware serial: Serial1

DFRobot_DF2301Q_UART asr(/*hardSerial =*/&Serial1);

#endif

I get the error

C:\Users\xxxx\Documents\Arduino\Voice_Module\Voice_Module.ino:29:43: note: suggested alternative: 'Serial'
DFRobot_DF2301Q_UART asr(/*hardSerial =*/&Serial);
                                          ^~~~~~~
                                          Serial

exit status 1

Compilation error: 'Serial1' was not declared in this scope

I commented out each line except 
DFRobot_DF2301Q_UART asr(/*hardSerial =*/&Serial1);

And changed "Serial1" to "Serial"

That worked and the sketch uploaded ok - however on the serial monitor it constantly says

16:41:59.440 -> Begin ok!

16:41:59.440 -> ������
�����
��
�������
�������_�

Even when the device isn't connected.

Something obviously isn't right - does anyone have working code and connection instructions for the Nano?  I've been searching for a few days now.

Many thanks,
Mike