不知道为什么，PulseAudio在Debian 11出现了无声音输出的问题，主要日志表现有：
1、Pulseaudio服务出现org.freedesktop.DBus.Error.NoReply：
systemctl --user --no-pager -l status pulseaudio.service
● pulseaudio.service - Sound Service
Loaded: loaded (/usr/lib/systemd/user/pulseaudio.service; enabled; vendor preset: enabled)
Active: active (running) since Fri 2023-01-06 16:29:31 CST; 2min 28s ago
TriggeredBy: ● pulseaudio.socket
Main PID: 217228 (pulseaudio)
Tasks: 2 (limit: 76768)
Memory: 7.2M
CPU: 169ms
CGroup: /user.slice/user-1000.slice/user@1000.service/app.slice/pulseaudio.service
└─217228 /usr/bin/pulseaudio --daemonize=no --log-target=journal
Jan 06 16:29:30 debian11 systemd[1122]: Starting Sound Service...
Jan 06 16:29:31 debian11 systemd[1122]: Started Sound Service.
Jan 06 16:29:56 debian11 pulseaudio[217228]: GetManagedObjects() failed: org.freedesktop.DBus.Error.NoReply: Did not receive a reply. Possible causes include: the remote application did not send a reply, the message bus security policy blocked the reply, the reply timeout expired, or the network connection was broken.2、VirtualBox启动虚拟机无声音，并弹出HostAudioNotResponding：
Host audio backend (PulseAudio) initialization has failed. Selecting the NULL audio backend with the consequence that no sound is audible.
Error ID:
HostAudioNotResponding
Severity:
Warning其VBox.log有一句话引起了注意：
PulseAudio: Failed to connect to server: Connection refused
3、syslog也出现org.freedesktop.DBus.Error.NoReply，不过更明确点是蓝牙模块引起。
cat /var/log/syslog |grep udio
Jan 6 16:22:09 debian11 dbus-daemon[702]: [system] Activating via systemd: service name='org.bluez' unit='dbus-org.bluez.service' requested by ':1.807' (uid=1000 pid=216065 comm="/usr/bin/pulseaudio --daemonize=no --log-target=jo")
Jan 6 16:22:34 debian11 pulseaudio[216065]: GetManagedObjects() failed: org.freedesktop.DBus.Error.NoReply: Did not receive a reply. Possible causes include: the remote application did not send a reply, the message bus security policy blocked the reply, the reply timeout expired, or the network connection was broken.4、pacmd命令查看pulseaudio状态，确实载入了蓝牙模块：
pacmd dump | grep module-bluetooth
load-module module-bluetooth-policy
load-module module-bluetooth-discover查找一番后，发现这是两个问题联合导致的：
1、PulseAudio蓝牙支持问题导致GetManagedObjects() failed: org.freedesktop.DBus.Error.NoReply。
2、PulseAudio authentication cookie问题导致VirtualBox连接PulseAudio出现Connection refused类型的HostAudioNotResponding。
所以解决问题主要是暂时禁用蓝牙模块（如果有需要）和配置正确的本地连接认证。
以下命令不需要root身份，需要的是当前登录用户身份。
以下假设当前登录用户名称为“test987654321”，其home目录为：“/home/test987654321”。
第一步：复制两份配置文件到当前登录用户目录下：
cp /usr/share/gdm/default.pa ~/.config/pulse/default.pa
cp /etc/pulse/client.conf ~/.config/pulse/client.conf第二步：修改~/.config/pulse/default.pa，禁用蓝牙模块
找到load-module module-bluetooth相关字样，然后全部在前面加#变成注释，即修改为：
#load-module module-bluetooth-policy
#load-module module-bluetooth-discover以下命令也能达到以上效果：
sed -Ei '/load-module module-bluetooth*/s/^/#/' ~/.config/pulse/default.pa
第三步：修改~/.config/pulse/default.pa，配置PulseAudio服务端本地连接认证【4】
找到：
load-module module-native-protocol-unix将它改为：
load-module module-native-protocol-unix socket=/home/test987654321/.config/pulse/socket-instance auth-cookie=/home/test987654321/.config/pulse/cookie auth-cookie-enabled=true（/home/test987654321请修改为实际的当前用户home目录）
第四步：修改~/.config/pulse/client.conf，配置PulseAudio客户端本地连接认证
添加如下内容：
default-server = unix:/home/test987654321/.config/pulse/socket-instance
cookie-file = /home/test987654321/.config/pulse/cookie（/home/test987654321请修改为实际的当前用户home目录）
第五步：重启PulseAudio服务（建议保存为脚本文件）：
systemctl --user mask pulseaudio.socket
systemctl --user stop pulseaudio.socket
systemctl --user stop pulseaudio.service
systemctl --user unmask pulseaudio.socket
systemctl --user start pulseaudio.service
systemctl --user status pulseaudio.service
参考资料：
【1】https://wiki.debian.org/PulseAudio
【2】Gentoo Forums :: 阅读主题 – [SOLVED] Pulseaudio for multi-user Linux：https://forums.gentoo.org/viewtopic-t-1110600-start-0.html
【3】[Solved] No sound in VirtualBox guest (Windows 7) / Multimedia and Games / Arch Linux Forums：https://bbs.archlinux.org/viewtopic.php?id=221934