diff --git a/Sources/OEVoice/AVSpeechSynthesizer-IPASpeech-extension.swift b/Sources/OEVoice/AVSpeechSynthesizer+speakIPA.swift
similarity index 93%
rename from Sources/OEVoice/AVSpeechSynthesizer-IPASpeech-extension.swift
rename to Sources/OEVoice/AVSpeechSynthesizer+speakIPA.swift
index 03e9b56..63d9fb3 100644
--- a/Sources/OEVoice/AVSpeechSynthesizer-IPASpeech-extension.swift
+++ b/Sources/OEVoice/AVSpeechSynthesizer+speakIPA.swift
@@ -1,6 +1,6 @@
 //
-//  AVSpeechSynthesizer-IPASpeech-extension.swift
-//  Wordhord
+//  AVSpeechSynthesizer+speakIPA.swift
+//  OEVoice
 //
 //  Created by Ryan Lintott on 2020-07-28.
 //
@@ -9,7 +9,7 @@ import Foundation
 import AVFoundation
 
 @available(iOS 10.0, *)
-extension AVSpeechSynthesizer {
+public extension AVSpeechSynthesizer {
     func speakIPA(_ ipaString: String, voiceIdentifier: String, willSpeak: ((String) -> Void)? = nil) {
         //Set the audio session to playback to ignore mute switch on device
         do {
diff --git a/Sources/OEVoice/OEVoice+AVFoundation.swift b/Sources/OEVoice/OEVoice+AVFoundation.swift
new file mode 100644
index 0000000..7aacd62
--- /dev/null
+++ b/Sources/OEVoice/OEVoice+AVFoundation.swift
@@ -0,0 +1,51 @@
+//
+//  OEVoice+AVFoundation.swift
+//  OEVoice
+//
+//  Created by Ryan Lintott on 2021-07-29.
+//
+
+import Foundation
+import AVFoundation
+
+@available(iOS 10.0, *)
+extension OEVoice {
+    public var shortIdentifier: String {
+        switch self {
+        case .siriMarthaGBcompact:
+            if #available(iOS 14.5, *) {
+                return "siri_Martha_en-GB_compact"
+            } else {
+                return "siri_female_en-GB_compact"
+            }
+        case .siriArthurGBcompact:
+            if #available(iOS 14.5, *) {
+                return "siri_Aurthur_en-GB_compact"
+            } else {
+                return "siri_male_en-GB_compact"
+            }
+        case .siriNickyUScompact:
+            if #available(iOS 14.5, *) {
+                return "siri_Nicky_en-US_compact"
+            } else {
+                return "siri_female_en-US_compact"
+            }
+        case .siriAaronUScompact:
+            if #available(iOS 14.5, *) {
+                return "siri_Aaron_en-US_compact"
+            } else {
+                return "siri_male_en-US_compact"
+            }
+        case .danielGBcompact:
+            return "Daniel-compact"
+        }
+    }
+    
+    public var identifier: String {
+        return "com.apple.ttsbundle.".appending(shortIdentifier)
+    }
+    
+    public var voice: AVSpeechSynthesisVoice? {
+        AVSpeechSynthesisVoice(identifier: identifier)
+    }
+}
diff --git a/Sources/OEVoice/OEVoice.swift b/Sources/OEVoice/OEVoice.swift
index a76c506..166466b 100644
--- a/Sources/OEVoice/OEVoice.swift
+++ b/Sources/OEVoice/OEVoice.swift
@@ -10,64 +10,38 @@ import AVFoundation
 
 @available(iOS 10.0, *)
 public enum OEVoice: CaseIterable {
-    // Default UK voices - Daniel
-    // Default UK siri voices - Martha, Arthur
-    // Default US voices - Fred, Samantha
-    // Default US siri voices - Nicky, Aaron
-    // Extra UK voices - Kate, Oliver, Serena
-    // Extra US voices - Alex, Allison, Ava, Nicky, Susan, Tom, Victoria
+    
+    // Default UK voice
+    case danielGBcompact
+    
+    // Default UK Siri voices (not available on macOS or simulator)
     case siriMarthaGBcompact
     case siriArthurGBcompact
-    case siriNickyUScompact
-    case siriAaronUScompact
+    
+    // Premium UK Siri voices (not on device by default and not available on macOS or simulator)
 //    case siriMarthaGBpremium
 //    case siriArthurGBpremium
+    
+    // Extra UK voices - Kate, Oliver, Serena (not on device by default)
+    
+    // Default US voices - Fred, Samantha
+    
+    // Default US Siri voices (not available on macOS or simulator)
+    case siriNickyUScompact
+    case siriAaronUScompact
+    
+    // Premium US Siri voices (not on device by default and not available on macOS or simulator)
 //    case siriNickyUSpremium
 //    case siriAaronUSpremium
-    case danielGBcompact
+    
+    // Extra US voices - Alex, Allison, Ava, Nicky, Susan, Tom, Victoria (not on device by default)
     
     #if targetEnvironment(simulator)
-    static let `default` = OEVoice.danielGBcompact
+    public static let `default` = OEVoice.danielGBcompact
     #else
-    static let `default` = OEVoice.siriNickyUScompact
+    public static let `default` = OEVoice.siriNickyUScompact
     #endif
     
-    private var identifier: String {
-        let prefix = "com.apple.ttsbundle."
-        switch self {
-        case .siriMarthaGBcompact:
-            return prefix.appending("siri_Martha_en-GB_compact")
-        case .siriArthurGBcompact:
-            return prefix.appending("siri_Aurthur_en-GB_compact")
-        case .siriNickyUScompact:
-            return prefix.appending("siri_Nicky_en-US_compact")
-        case .siriAaronUScompact:
-            return prefix.appending("siri_Aaron_en-US_compact")
-        case .danielGBcompact:
-            return prefix.appending("Daniel-compact")
-        }
-    }
-    
-    private var legacyIdentifiers: [String] {
-        let prefix = "com.apple.ttsbundle."
-        switch self {
-        case .siriMarthaGBcompact:
-            return [prefix.appending("siri_female_en-GB_compact")]
-        case .siriArthurGBcompact:
-            return [prefix.appending("siri_male_en-GB_compact")]
-        case .siriNickyUScompact:
-            return [prefix.appending("siri_female_en-US_compact")]
-        case .siriAaronUScompact:
-            return [prefix.appending("siri_male_en-US_compact")]
-        default:
-            return []
-        }
-    }
-    
-    public var voice: AVSpeechSynthesisVoice? {
-        AVSpeechSynthesisVoice(identifier: identifier) ?? legacyIdentifiers.compactMap { AVSpeechSynthesisVoice(identifier: $0) }.first
-    }
-    
     public func speak(_ ipaString: String, synthesizer: AVSpeechSynthesizer) {
         synthesizer.speakIPA(adjustIPAString(ipaString), voiceIdentifier: identifier)
     }
diff --git a/Sources/OEVoice/SpecialCharacter.swift b/Sources/OEVoice/SpecialCharacter.swift
index 6288fde..f2e5384 100644
--- a/Sources/OEVoice/SpecialCharacter.swift
+++ b/Sources/OEVoice/SpecialCharacter.swift
@@ -1,6 +1,6 @@
 //
 //  SpecialCharacter.swift
-//  TextToSpeech
+//  OEVoice
 //
 //  Created by Ryan Lintott on 2021-06-23.
 //
diff --git a/Sources/OEVoice/extensions/String-extensions.swift b/Sources/OEVoice/extensions/String-extensions.swift
new file mode 100644
index 0000000..4e12699
--- /dev/null
+++ b/Sources/OEVoice/extensions/String-extensions.swift
@@ -0,0 +1,30 @@
+//
+//  String-extensions.swift
+//  Wordhord
+//
+//  Created by Ryan Lintott on 2020-11-06.
+//
+
+import SwiftUI
+
+internal extension String {
+    func droppingSuffix<S: StringProtocol>(_ string: S) -> String {
+        guard self.hasSuffix(string) else { return String(self) }
+        return String(self.dropLast(string.count))
+    }
+    
+    func droppingPrefix<S: StringProtocol>(_ string: S) -> String {
+        guard self.hasPrefix(string) else { return String(self) }
+        return String(self.dropFirst(string.count))
+    }
+    
+    func replacingSuffixOccurrence(of string: String, with replacement: String) -> String {
+        guard self.hasSuffix(string) else { return self }
+        return self.droppingSuffix(string).appending(replacement)
+    }
+    
+    func replacingPrefixOccurrence(of string: String, with replacement: String) -> String {
+        guard self.hasPrefix(string) else { return self }
+        return replacement.appending(self.droppingPrefix(string))
+    }
+}