## 4 Discussion
To better understand L2 speech acquisition, future studies should consider employing both production and perception tasks with the same group of participants to explore the potential link between L2 speech production and perception. More specifically, discrimination or identification tasks can be implemented to study the perceptive abilities of L2 learners on non-native tones (e.g., [45; 46]). Furthermore, the L1 background of the L2 participants in this study was homogeneous, as they were all native speakers of Mandarin without knowledge of any other Chinese languages before coming to Hong Kong. The participants' homogeneous background limited the scope of potential generalisation of our findings. For instance, ref. [28] found that L2 speakers with different dominant languages may produce Cantonese tones differently, and ref. [47] suggested that quantity and quality of input across different settings should also be considered as a key feature of learners' background. To provide a more complete picture of L2 Cantonese tone acquisition, it would be worthwhile for future studies to recruit L2 participants with a greater variety of L1 backgrounds (e.g., speakers of other tonal languages or non-tonal languages) and different degrees of exposure to Cantonese. Inclusion of learners with various L1s also increases the generalisability of the main findings. In conclusion, this study provided acoustic and perceptual data pertaining to Mandarin-speaking immigrants' Cantonese tone production and demonstrated some relationship between the acoustic and perceptual measurements. In general, the Mandarinspeakers' tones were non-native-like despite having received sufficient exposure to Cantonese input and being categorised as advanced learners of Cantonese. The findings add to the existing literature on learning L2 speech and support the hypotheses of current speech learning models. Future research is needed to investigate L2 tone acquisition with both production and perception data obtained from participants with more diverse L1s. The following supporting information can be downloaded at [[https://www.mdpi.com/article/10.3390/app15126590/s1](https://www.mdpi.com/article/10.3390/app15126590/s1)]([https://www.mdpi.com/article/10.3390/app15126590/s1](https://www.mdpi.com/article/10.3390/app15126590/s1)). Table S1: Raw and converted F0 data; Table S2: Raw rating data. Conceptualisation, Y.Y. ; methodology, Y.Y. ; formal analysis, J.H., Y.Y. and Y.Z. ; investigation, D.H. and Y.Y. ; writing\(-\)original draft preparation, J.H. and Y.Y. ; writing\(-\)review and editing, D.H., J.H., Y.Y. and Y.Z. ; visualisation, J.H. ; supervision, Y.Y. ; project administration, Y.Y. ; funding acquisition, Y.Y. All authors have read and agreed to the published version of the manuscript. This research was funded by the Research Grants Council of the Hong Kong Special Administrative Region, grant number UGC/FDS15/H15/22, and the Acoustical Society of America to Y.Y. The APC was partially supported by the Research Grants Council of the Hong Kong Special Administrative Region. The study was conducted in accordance with the Declaration of Helsinki, and approved by the Human Research Ethics Committee of Hong Kong Shue Yan University (protocol code: HREC 22-05 (M12); data of approval: 1 June 2022). Informed Consent Statement: Informed consent was obtained from all subjects involved in the study. The original contributions presented in this study are included in the Supplementary Materials. Further inquiries can be directed to the corresponding author. The authors would like to thank all the informants for their participation in this study. An earlier version of this manuscript was presented at the 20 th International Congress of the Phonetic Sciences and published in its proceedings [48]. The authors are grateful to the audience for their helpful comments, especially those from [PERSON], [PERSON], [PERSON], [PERSON], [PERSON], [PERSON], and [PERSON]. The authors declare no conflicts of interest.