### The Motivation of the Current Study  
Ref. [14] proposed for the first time that the F0 range of a speaker could be estimated from a set of spectral parameters of a very brief speech signal using the LSTM-based model. The model can in a sense mimic the human auditory mechanism of pitch perception. Nevertheless, there are still questions or flaws about the model, which motivate the current study.  
For one thing, the measurement of F0 range with two parameters (the mean and standard deviation of F0) adopted in [14] is still debatable. This measurement is inherently associated with the assumption that the distribution of F0 is symmetric about the mean F0, as illustrated in Figure 1a, which however does not always coincide with the actual situation.  
Previous studies found that the distribution of F0 above and below the mean was not really symmetric, with the upper interval wider than the lower interval [44]. In [26], results from a passage reading showed that the distance between mean F0 and floor F0 was smaller than that between ceiling F0 and mean F0. Moreover, the spectral characteristics for the upper and lower limits of F0 range were different. As reviewed in [7], falsetto and tense voice are associated with the perceptual upper limit of pitch, whereas creaky voice is associated with the perceptual lower limit of pitch. These suggest that quantifying the F0 span simply with a standard deviation is not adequate. Therefore, we further modified the model by substituting the estimation of the ceiling and floor F0s as shown in Figure 1b for the estimation of the standard deviation as shown in Figure 1a. In this way, there are three parameters in total which need to be estimated.  
For another, it is unclear whether the model inherently estimated the surface F0 range of the present sample of running speech, or the speaker-specific underlying F0 range regardless of the linguistic and paralinguistic information conveyed in the present speech sample. In other words, it needs to be testified whether the estimated F0 range is closer to the surface F0 range or the underlying F0 range.  
Since the underlying F0 range reflects the physiological traits of the speaker, it is deemed to be independent of the language being spoken. In contrast, the literature has shown that the surface F0 range of speech may vary systematically with language, depending on the phonological nature of the spoken language. For example, [26] found that the native speakers of Mandarin and English differed significantly in the speaking F0 range. [17] reported that English speech had a wider speaking F0 range than German speech. Moreover, [46; 47] revealed that a speaker tended to have differing F0 manifestations when speaking different languages.  
Therefore, a way to answer the question is to test the model on bilingual speech data from the same speaker to find out whether the estimated F0 ranges vary with the language being spoken.  
With the above two motivations, we designed two experiments, with the first to refine the model setting, and the second to testify the estimation of underlying F0 range.  
Figure 1: The measurement of F0 range: (**a**) in the initial model; (**b**) in the refined model.