Как исправить задержку в приложении синтеза речи?

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Я написал приложение на Visual Basic 2017, которое должно было помочь мне понять синтез речи. Приложение работает нормально, за исключением одной вещи, есть 1-2 - секундная задержка в разговорной части во время первой итерации, но не в последующих итерациях. Мы ничего не слышим, пока заявление не будет сделано наполовину. Что я упускаю?
Код включен здесь:

Imports System.Speech.Synthesis

Public Class Form1

    Dim synth As New SpeechSynthesizer()
    Dim prompt1 As String = ""
    Dim prompt2 As String = ""
    Dim user As String = "Darby"
    Dim currentTime As Date = TimeOfDay
    Dim Sayit1 As String = ""
    Dim Sayit2 As String = ""
    Dim greeting1 As String = ""
    Dim greeting2 As String = ""


    Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
        greeting1 = "Hi " & user & ", "
        If currentTime >= #12:00:00 AM# And currentTime < #12:00:00 PM# Then
            greeting2 = " How is your Morning going?"
        ElseIf currentTime >= #12:00:00 PM# And currentTime < #6:00:00 PM# Then
            greeting2 = " How is your Afternoon going?  "
        ElseIf currentTime >= #6:00:00 PM# Then
            greeting2 = " How is your Evening going? "
        End If
        TalkToMe(greeting1, greeting2)
    End Sub
    Private Sub Button2_Click(sender As Object, e As EventArgs) Handles Button2.Click
        greeting1 = "Goodbye " & user & ", "
        If currentTime >= #12:00:00 AM# And currentTime < #12:00:00 PM# Then
            greeting2 = " you Have a Good Morning  "
        ElseIf currentTime >= #12:00:00 PM# And currentTime < #6:00:00 PM# Then
            greeting2 = " you Have a Blessed Afternoon "
        ElseIf currentTime >= #6:00:00 PM# Then
            greeting2 = " you Have a Good Evening "
        End If
        TalkToMe(greeting1, greeting2)
    End Sub


    Private Sub Button4_Click(sender As Object, e As EventArgs) Handles Button4.Click
        Sayit1 = TextBox1.Text
        TalkToMe(Sayit1, "")
    End Sub

    Private Sub TalkToMe(prompt1, prompt2)
        synth.SelectVoice("Microsoft David Desktop")
        synth.Volume = 40
        synth.Rate = -1
        synth.Speak(prompt1 + prompt2)
        prompt1 = ""
        prompt2 = ""
    End Sub

    Private Sub Button3_Click(sender As Object, e As EventArgs) Handles Button3.Click
        End
    End Sub

End Class

Что я уже пробовал:

Я переместил последовательность инициализации в разные позиции, но задержка одна и та же. (т:

synth.SelectVoice("Microsoft David Desktop")
   synth.Volume = 40
   synth.Rate = -1

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