内容来源：https://www.engadget.com/2246402/improve-audio-quality-apple-carplay/

内容总结：

提升苹果CarPlay音质的实用指南

苹果CarPlay为驾车时播放Spotify或Apple Music音乐提供了便捷方案，但默认设置未必能发挥车载音响的全部潜力。由于手机与车载系统的连接方式、音频设置及音源质量均会影响最终听感，无需急于升级硬件，通过以下简单调整即可显著改善音质。

有线连接是实现无损音质的首选
尽管无线CarPlay更为便利，但苹果官方明确表示，只有通过USB有线连接才能播放无损音频。无线连接需采用AAC-LC编码进行有损压缩，会丢失部分原始音频数据；而有线连接使用LPCM传输，可完整保留Apple Music的ALAC无损格式。若需体验最佳音质，建议使用有线连接，并确保在Apple Music中开启无损选项。

下载高质量音乐，避免流量波动影响
驾车途中移动网络信号不稳定，可能导致流媒体音质自动下降。解决方法是出发前将常用歌单下载至iPhone。Apple Music支持下载24-bit/48kHz无损音质，Spotify高级用户亦可下载FLAC格式无损音频。注意无损文件占用存储空间较大，且下载前需在设置中手动选择最高音质，并删除旧版低质量文件。

检查均衡器与音量设置
各音乐应用的音效设置对车载听感影响显著。Apple Music的均衡器（EQ）预设可能针对耳机优化，在车内反而效果不佳，建议关闭或尝试其他预设。同时可开启“声音检查”功能，自动平衡曲目间音量差异。调整后应逐一试听，避免多次修改后难以判断实际效果。

警惕CarPlay音效异常Bug
若CarPlay突然失去低音、音量或清晰度，可能是语音播报后的“音量降低”功能卡顿所致。可尝试通过方向盘按键激活Siri后立即再次按下取消，多数车主反馈（包括马自达、保时捷、斯巴鲁、福特、丰田等）此方法有效。若问题持续，可通过“设置>通用>CarPlay”删除车辆配对并重新连接，以重置冲突设置。

结论：从源头优化，逐步试验
提升车载音质的核心在于先获取高解析度音源，再搭配有线连接和无损播放，同时校准应用内音频设置。但需注意，车辆扬声器、功放及行驶噪音对音质影响极大，建议每次仅调整一项设置，并仔细聆听对比，以找到最适合自身爱车的组合。

中文翻译：

如何提升Apple CarPlay的音频质量
CarPlay非常适合在旅途中听音乐，但一些小小的调整能帮助它在你的车里呈现更出色的音效。
Apple CarPlay为你提供了一个便捷的方案，让你可以在车内播放Spotify或Apple Music中喜爱的音乐。然而，它并不能保证给你爱车能呈现的最佳音质。你的iPhone可能会向车载音响传输比你预期更低质量的音频流，某些设置戴耳机听效果不错，但通过汽车扬声器播放却糟透了。
考虑到不同汽车扬声器之间存在巨大差异，这个问题没有神奇的解决方案。原始音乐的质量显然会起到作用，但你的iPhone与汽车的连接方式同样有影响。与其急着升级扬声器系统，不如先尝试一些简单的调整来提升使用Apple CarPlay时的音频质量。
有线CarPlay可带来无损音频
对大多数人来说，无线CarPlay是最便捷的选择。你甚至不需要把iPhone从口袋里拿出来，汽车就能连接并开始播放你喜爱的歌曲。遗憾的是，对于追求最佳音质的人来说，这并不是最佳选项。
听听苹果怎么说：有线连接对音乐最有利。苹果关于通过CarPlay使用Apple Music的指南确认，只有有线USB连接才能播放无损音频。无损音频在压缩时不会丢弃任何原始音频数据，意味着你不会损失细节。有线连接意味着你可以切换到无损音频流，只要你拥有有效的Apple Music订阅并已启用该选项。
从技术上讲，这一切都归结于编解码器。苹果在有线CarPlay连接上使用LPCM传输音频，而在使用无线CarPlay时则切换到AAC-LC。LPCM承载未压缩的数字音频，因此来自Apple Music的无损ALAC曲目可以无需有损压缩直接传输到你的汽车。无线CarPlay则必须先将音频编码为AAC-LC，使用有损压缩来降低比特率，过程中会丢弃部分原始音频数据。
最终结果是音质有所下降，但这并不意味着无线CarPlay听起来就一定差。你是否能听出区别，取决于你汽车音响系统的品质和你的耳朵。扬声器和功放（如果你的车有的话）对此影响巨大。此外，其他干扰因素，比如路噪，永远不会为听音乐提供理想的环境。
出发前下载高质量音乐
有线连接只能保留它接收到的音质。当你在开车时从Apple Music或Spotify流媒体播放，你的移动网络连接不可能始终完美。你会频繁在信号塔之间切换，不断进出蜂窝网络覆盖范围。连接中断意味着音质下降：CarPlay无法弥补这一点，即使通过USB连接也不行。
这个问题很容易解决：出发前将你常听的播放列表下载到iPhone上。Apple Music让你可以选择偏好的下载音质设置，包括24位/48kHz的无损格式。搭配有线CarPlay使用，这将为你带来该平台上最佳的音质。如果你之前以较低音质下载过音乐，苹果建议将其从手机中删除并重新下载，以获得无损版本。
你也可以在其他平台上收听无损音频，包括Spotify，它允许Premium订阅者以24位/44.1kHz的FLAC格式下载无损音频。否则，Spotify会根据你的网络连接自动调整流媒体播放质量；下载播放列表可以避免这种情况发生。
由于无损音频文件比压缩格式占用更多存储空间，请确保你的设备有足够的空间。下载音乐的另一个好处是节省你的流量套餐，因为无损流媒体播放会消耗大量数据。
检查iPhone上的均衡器和音量设置
所选流媒体应用的音频设置也是另一个值得检查的方面。如果你的音乐听起来刺耳、异常单薄或者低音过重，音量控制和均衡器设置可以提供帮助。
Apple Music有自己的均衡器设置，你可以通过“设置”>“应用”>“音乐”>“均衡器”进入。你可能已经选择了一个预设；如果是这样，请关闭均衡器再听一次，比较一下效果。适合耳机的预设在你通过汽车扬声器系统听音乐时，效果可能完全不同。
Apple Music还有一个“声音检查”模式，这是一项归一化功能，会自动调整播放音量。如果一首歌太轻或太响，“声音检查”会根据其对感知响度的测量来尝试均衡音量。你可以通过点击“设置”>“应用”>“音乐”来设置，并切换“声音检查”的开关。其他音乐应用可能也有自己的均衡器或音量归一化设置，你也需要检查一下。
每次进行更改后，最好通过重新听音乐立即检查效果。不要一次更改多个选项后再做比较，因为你将无法准确与原来的设置进行对比，如果需要的话，也不容易轻松改回去。
警惕这个不常见的CarPlay故障
如果CarPlay通常听起来正常，但突然失去了低音、音量或清晰度，那么一个奇怪的音频闪避故障可能就是罪魁祸首。每当Siri或导航应用说话时，CarPlay必须降低音量，而用户反映音乐有时会卡在这种降低音量的状态中。
这个持续多年的Reddit帖子中提到了一种常见的解决方法。尝试通过方向盘控制激活Siri，然后立即再次按下按钮将其关闭。该帖子中包含了马自达、保时捷、斯巴鲁、福特、丰田等车主的反馈，表明这样做能让他们的音乐恢复正常。
其他故障也可能出现；在这种情况下，如果Apple CarPlay无法正常工作，值得移除设备并重新配对。全新的连接通常会重置任何冲突的设置，恢复正常的运行状态。你可以通过“设置”>“通用”>“CarPlay”，选择你的汽车，然后点击“忽略此车”来完成。
尽可能为CarPlay提供最佳音源
如果你想在车内获得最佳音质，你需要最高质量的源音频。有线CarPlay连接效果最好，但你仍然需要切换到Apple Music或Spotify中的无损播放模式，以消除降低质量的压缩。出发前以无损格式下载文件，可以避免流媒体播放的不稳定性。你配置的任何音频设置，尤其是流媒体应用中的自定义均衡器，都值得再次确认。
不过，仅靠调整一些设置所能达到的效果是有限的。你的扬声器配置，包括功放，会对音质产生很大影响。驾驶时车内的声学环境也有重大影响。在这种情况下，多做实验是最好的选择：一次只做一个更改，仔细聆听看看是否带来足够大的差异。

英文来源：

How to improve your audio quality on Apple CarPlay
CarPlay is great for listening to music on the go, but a few tweaks will help it sound even better in your car.
Apple CarPlay gives you an easy solution for playing your favorite music from Spotify or Apple Music in your vehicle. However, it isn't guaranteed to give you the best sound your car can produce. Your iPhone might feed the stereo a lower-quality stream than you expect, with settings that sound great through your headphones but awful through your car speakers.
There's no magic solution for this, given how much variance there is between car speakers. The quality of the original music will obviously play its part, but the way your iPhone connects to your car has an impact, too. Rather than upgrading your speaker system right away, you can try some straightforward changes to improve the audio quality when using Apple CarPlay.
Wired CarPlay gives you lossless audio
Wireless CarPlay is the most convenient option for most people. You don't even have to get your iPhone out of your pocket for your car to connect and start playing your favorite songs. Unfortunately, it isn't the best option for those who demand the best music quality.
Take it from Apple: wired is best for your music. Apple's guidelines for Apple Music through CarPlay confirm that only a wired USB connection will allow you to play lossless audio. Lossless audio is compressed without throwing away any of the original audio data, meaning you're not losing detail. A wired connection means you can switch to lossless streams, as long as you have an active Apple Music subscription and have enabled this option.
Technically, it's all down to the codec. Apple uses LPCM for audio on wired CarPlay connections, but switches to AAC-LC when using wireless CarPlay. LPCM carries uncompressed digital audio, so a lossless ALAC track from Apple Music can be passed to your car without lossy compression. Wireless CarPlay has to encode the audio into AAC-LC first, using lossy compression to reduce the bitrate and discarding some of the original audio data in the process.
The end result is lower-quality audio, but that doesn't mean wireless CarPlay automatically sounds bad. Whether you hear the difference will depend on your car's sound system and your ears. The speakers and amp (if your car has one) have a huge influence here. Plus, other distractions, like road noise, are never going to provide the perfect environment for listening to music.
Download high-quality music before you drive
A wired connection can only preserve the quality it receives in the first place. When you're streaming from Apple Music or Spotify while driving, your mobile connection isn't going to be perfect. You're regularly shifting between cell towers and dipping in and out of cellular coverage. Drops in connection mean drops in quality: CarPlay can't counter that, even over USB.
This problem is easily fixed by downloading your regular playlists to your iPhone before you set off. Apple Music lets you choose your preferred quality setting for downloads, including lossless at 24-bit/48kHz. This, while using wired CarPlay, will give you the best possible sound quality over the platform. If you've downloaded your music at a lower quality before, Apple recommends deleting it from your phone and downloading it again to get the lossless version.
You can listen to lossless audio on other platforms too, including Spotify, which allows Premium subscribers to download lossless audio at 24-bit/44.1kHz using FLAC. Otherwise, Spotify will automatically adjust your streaming quality per your connection; downloading your playlists will stop this from happening.
Because lossless audio files will take up significantly more storage than compressed equivalents, make sure you've got plenty of space available. Another benefit of downloading your music is preserving your data plan, since lossless streaming uses a huge amount of data.
Check the equalizer and volume settings on your iPhone
The audio settings for your chosen streaming app are another area to review. Volume control and equalizer settings can help if your music sounds tinny, strangely thin, or heavy on bass.
Apple Music has its own equalizer settings, which you can access through Settings > Apps > Music > EQ. You might have already chosen a preset; if so, turn the EQ off and listen again to see how it compares. A preset that works well with headphones probably won't sound the same while you're listening to music through a car's speaker system.
Apple Music also has a Sound Check mode, which is a normalization feature that automatically adjusts playback volume. If a song is too quiet or too loud, Sound Check will try to equalize the volume based on its own measure of perceived loudness. You can set this by tapping Settings > Apps > Music and toggling Sound Check on or off. Other music apps might have their own equalizer or volume normalization settings that you'll need to check, too.
After every change you make, it's best to check the impact immediately by listening to your music again. You don't want to compare after changing several different options, as you won't be able to accurately compare it to the original settings you used and, if needed, switch it back as easily.
Watch out for this unusual CarPlay bug
If CarPlay usually sounds OK but suddenly loses its bass, volume, or clarity, then an odd audio ducking bug might be the cause. CarPlay has to lower the volume whenever Siri or your maps app is speaking, and people have reported music can sometimes get stuck in this state afterwards.
A common workaround, mentioned in this long-running Reddit thread over the last few years, suggests a workaround. Try activating Siri using your steering wheel control, then immediately hitting the button again to dismiss it. The thread includes reports from Mazda, Porsche, Subaru, Ford, Toyota, and other owners suggesting that this restored their music to normal.
Other bugs may also crop up; in these cases, it's worth removing your device and re-pairing it if Apple CarPlay isn't working properly. A fresh connection will often reset any conflicting settings and restore normal working order. You can do this at Settings > General > CarPlay, selecting your car, then tapping Forget This Car.
Give CarPlay the best source you can
If you want the best audio quality in your car, you're going to need the highest-quality source audio. A wired CarPlay connection works best, but you'll still need to switch to lossless playback in Apple Music or Spotify to eliminate quality-reducing compression. Avoid the variability of streaming by downloading the files in lossless format before you set off. Any audio settings you've configured, especially custom EQs in streaming apps, are worth double-checking.
There's a limit to what you can achieve with just a few tweaks to your settings, though. Your speaker setup, including your amplifier, will have a big impact on quality. The acoustics in your car as you're driving have a major effect, too. Experimentation is your best bet here: make one change at a time and listen carefully to see if it makes a big enough difference.